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Health Canada

Protocols for Radon Measurements in Dwellings

Date 2006-11-30

Publication # etc

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ACKNOWLEDGEMENTS

Health Canada would like to thank the United States Environmental Protection Agency

for permission to quote from their radon guidance documents and for their assistance in

preparing this document.

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Table of Contents

ACKNOWLEDGEMENTS................................................................................................ 2

Table of Contents................................................................................................................ 3

Section 1:

Introduction................................................................................................. 5

1.1

Scope and Summary ........................................................................................... 5

1.2

Radon Guideline ................................................................................................. 5

Section 2:

Measurement Protocols..............................Error! Bookmark not defined.

2.1

Measurement Duration........................................................................................ 6

2.1.1

Long-term Measurements........................................................................... 6

2.1.2

Short-term Measurements........................................................................... 6

2.2

Measurement Locations...................................................................................... 6

2.3

Measurement Strategy ........................................................................................ 7

2.3.1

Initial Measurement .................................................................................... 7

2.3.2

Closed-building Conditions for Short-term Measurements........................ 7

2.4

Interpretation of Initial Measurement Results .................................................... 8

2.4.1

Long-term Measurements........................................................................... 8

2.4.2

Short-term Measurements........................................................................... 8

2.5

Interpretation of Follow-up Measurement Results ............................................. 8

2.6

Measurements in Public Buildings ..................................................................... 9

2.6.1

Measurement Location in Public Buildings................................................ 9

2.6.2

Interpretation of Measurement Results in Public Buildings..................... 10

2.6.2.1

Long-term Measurements

10

2.6.2.2

Short-term Measurements 10

2.7

Measurements in Schools and Daycare Centres............................................... 10

2.7.1

Measurement Location in Schools and Daycare Centres ......................... 10

2.7.2

Follow-up Measurements.......................................................................... 11

2.7.3

Interpretation of School Measurement Results......................................... 11

Section 3:

Measurements for Real-Estate Transactions............................................. 12

3.1

Introduction....................................................................................................... 12

3.1.1

Measurement Location for Real Estate Transactions ............................... 12

3.2

Options for Real-Estate Measurements ............................................................ 13

3.2.1

Option 1: Passive Device Measurement ................................................... 13

3.2.1.1 Interpretation of Passive Device Measurement Results........................ 13

3.2.2

Option 2: Active Device Measurement..................................................... 14

3.2.2.1 Interpretation of Active Device Measurement Results......................... 14

3.2.3

Measurement Interference ........................................................................ 15

3.2.3.1 Influencing Measurement Area Concentration..................................... 15

3.2.3.2 Equipment Interference......................................................................... 15

3.2.4

Preventing Interferences ........................................................................... 15

Section 4:

General Procedural Recommendations..................................................... 17

4.1

Real-Estate Measurements................................................................................ 17

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4.1.1

Initial Client Interview.............................................................................. 17

4.1.2

Conditions for a Valid Measurement........................................................ 18

4.1.3

Anti-Interference Documentation............................................................. 18

4.2

Measurements by Clients.................................................................................. 18

4.3

Documentation.................................................................................................. 18

4.3.1

Measurement Log ..................................................................................... 18

4.4

Quality Assurance in Radon Measurements..................................................... 19

4.4.1

Quality Assurance Plans........................................................................... 19

4.4.2

Standard Operating Procedures................................................................. 19

4.4.3

Calibration Measurements........................................................................ 19

4.4.4

Known Exposure Measurements .............................................................. 20

4.4.5

Background (Blank) Measurements ......................................................... 20

4.4.6

Field Controls............................................................................................ 20

4.4.6.1 Field Blanks.......................................................................................... 20

4.4.6.2 Field Duplicates.................................................................................... 20

4.4.7

Instrument Performance Checks............................................................... 21

4.4.8

Reporting Results...................................................................................... 21

4.4.9

Recommendations for Remedial Action................................................... 21

4.5

Worker Safety................................................................................................... 22

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Section 1: Introduction

1.1 Scope and Summary

The intended audience for this document includes radon

*

survey planners and persons

who intend to carry out radon measurements to identify dwellings for remedial action

against radon. The scope is limited to guidance regarding measurement device placement,

measurement duration, multiple measurements, and the interpretation of measurement

results.

Section 1 of this document provides an overview of the Canadian Radon Guideline.

Section 2 of this document provides protocols for initial radon concentration

measurements in dwellings intended to guide decisions on the need for remedial actions

to reduce the radon concentration.

Section 3 of this document provides protocols for measuring radon for a real-estate

transaction. These protocols were developed to deal with the time-sensitive nature of

home sales and purchases, while still assuring the buyer that the measurement of radon

concentrations in the building is valid.

Section 4 of this document provides general guidance on the implementation of these

protocols and on the quality assurance planning needed to produce valid measurements.

1.2 Radon Guideline

The following guideline was adopted by the Federal-Provincial-Territorial

Radiation Protection Committee on October 26, 2006:

“Remedial measures should be undertaken in a dwelling whenever the

average annual radon concentration exceeds 200 Bq/m

3

in the normal

occupancy area.

The higher the radon concentration, the sooner remedial measures should be

undertaken.

When remedial action is taken, the radon level should be reduced to a value

as low as practicable.

The construction of new dwellings should employ techniques that will

minimize radon entry and will facilitate post-construction radon removal,

should this subsequently prove necessary.”

*

The term "radon" refers to both Radon-222 and its decay products unless otherwise noted.

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1.3 Measurement Duration

1.3.1 Long-term Measurements

Long-term measurements can range from 91 to 365 days (typically 3 to 6 months) to

provide seasonal average radon concentration estimates. Once the measurement devices

are installed, there are no requirements for the occupants to change their life-style during

the measurement.

1.3.2 Short-term Measurements

Short-term measurements can range from 2 to 90 days but are typically 2 to 7 days. They

are made under closed-building conditions to stabilize the radon concentrations and

increase the validity of the annual radon concentration estimate. Closed-building

conditions generally prevail during the cold season from October to April when the

average daily temperature is low enough that windows are kept closed. In some houses,

the most stable radon levels occur during late fall and early spring, when windows are

kept closed but the house heating system (which causes some ventilation and circulation)

is not used.

To provide closed-building conditions outside the cold season, the occupants may have to

change their life-style for the duration of the measurement.

1.4 Measurement Locations

To provide a realistic estimate of the radon exposure of the occupants, all measurements

should be made in the normal occupancy area of the lowest lived-in level of the dwelling.

Potential measurement locations for both long and short-term measurements include

family rooms, living rooms, dens, playrooms and bedrooms. A lower level bedroom is

preferred because people generally spend more time in their bedrooms than in any other

room in the house. Similarly, if there are children in the home, lowest level bedrooms or

other areas such as a playroom are preferred.

• The preferred device location is by an interior wall at least 50 cm from the floor

and at least 10 cm from other objects. The optimal height is in the breathing zone

– 0.8 to 2 metres from the floor.

• Measurements should not be made in kitchens or laundry rooms. Kitchen exhaust

fan systems and airborne particles (caused by cooking) may affect some

measurement devices.

• Measurements should not be made in bathrooms because relatively little time is

spent in a bathroom, high humidity may affect some measurement devices, and

use of an exhaust fan may temporarily alter radon concentrations.

• Measurements should not be made in closets, cupboards, sumps, crawl spaces or

nooks within the foundation. Radon concentrations in these areas are not

representative of the concentration in the occupied area of the house.

The location should not be in air currents caused by heating, ventilating and air

conditioning vents, doors, fans and windows. Locations near heat, such as over radiators,

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near fireplaces or in direct sunlight, should be avoided as some measurement devices may

be affected.

1.5 Measurement Strategy

1.5.1 Initial Measurement

An initial measurement is required to determine whether the average radon concentration

in a dwelling is high enough to justify additional measurements or remedial measures. It

is common to see radon levels in a single house change by a factor of 2 to 3 over a one-

day period, and variations from season to season can be even larger. The highest levels

are usually during winter. A long-term measurement period will give a much better

indication of the annual average radon concentration than measurements of shorter

duration. For this reason, Health Canada recommends that the initial radon measurement

in a dwelling be a long-term measurement. If the result is greater than 200 Bq/m

3

, then

remedial action is recommended within the time frame suggested in the Guideline.

In some cases, however, a more rapid answer may be required, either as a screening

measurement to confirm that radon levels are low or to decide on the need for further

measurements. In these cases, short-term measurements lasting only a few days may

provide sufficient information. The measurement conditions should be chosen to

maximize the radon concentration (closed-building conditions). Wherever possible, short-

term measurements should be made during the cold season (i.e. October to April) when

radon levels are generally the highest.

1.5.2 Closed-building Conditions for Short-term Measurements

Closed-building conditions include:

• Windows on all levels and external doors should be kept closed, except during

normal entry and exit, during the measurement period. Normal entry and exit

include a brief opening and closing of a door, but external doors should not be left

open for more than a few minutes.

• External-internal air exchange systems such as high-volume, whole-house and

window fans should not be operated. However, attic fans intended to control attic

temperature or humidity may be operated. Combustion or furnace makeup air

supplies must not be closed.

• Normal operation of permanently installed energy recovery ventilators (also

known as heat recovery ventilators or air-to-air heat exchangers) may continue

during closed-building conditions. In houses where permanent radon mitigation

systems have been installed, these systems should be functioning during the

measurement period.

• Air conditioning systems that recycle interior air can be operated during the

closed-building conditions.

In addition to maintaining closed-building conditions during the measurement, closed-

building conditions are required for 12 hours prior to the start of the measurement for

measurements lasting less than four days, and are recommended prior to measurements

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lasting up to a week. When closed-building conditions are not the normal living

conditions, the measurement conditions must be maintained rigorously to ensure the

validity of the short-term measurement.

Short-term measurements lasting less than three days should not be conducted during

severe storms or periods of unusually high winds. The rapid changes in barometric

pressure associated with storms increase the chance of a large difference in the building

interior and exterior air pressures, thus changing the rate of radon influx. A high wind

increases the variability of radon concentration because of wind-induced differences in

air pressure between the building interior and exterior. In either case, the radon

concentration during the measurement may not be representative of the average

concentration in the building. Weather predictions available on local news stations

provide sufficient information to determine if these conditions are likely.

1.6 Interpretation of Initial Measurement Results

1.6.1 Long-term Measurements

If the long-term measurement result is below 200 Bq/m

3

, the average annual

concentration in the dwelling is probably below 200 Bq/m

3

and further measurements are

not necessary.

If the long-term measurement result is greater than 200 Bq/m

3

, then the average annual

concentration in the dwelling is probably above 200 Bq/m

3

and remedial action is

recommended.

1.6.2 Short-term Measurements

Since radon concentrations vary over time, it is suggested that the result of any short-term

measurement be confirmed with a “follow-up” long-term measurement. The follow-up

measurement should be made at the same location as the initial measurement.

If the initial short-term measurement result is below 200 Bq/m

3

, the average annual

concentration in the dwelling is probably below 200 Bq/m

3

. However, since radon levels

change over time, the homeowner may wish to confirm this with a long-term

measurement.

If the initial short-term measurement result is greater than 200 Bq/m

3

, the average annual

concentration may be above 200 Bq/m

3

, and a follow-up measurement with a long-term

method is recommended.

If the initial short-term measurement is greater than 600 Bq/m

3

, the follow-up

measurement may be made with a short-term method.

1.7 Interpretation of Follow-up Measurement Results

A single short-term measurement is not sufficient to base a decision to mitigate. A

follow-up measurement is always necessary for mitigation decision-making regardless of

the initial measurement result.

If the result of the long-term follow-up measurement is less than 200 Bq/m

3

, then

remedial action is not necessary.

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If the result of the long-term follow-up measurement is greater than 200 Bq/m

3

, then

remedial action is recommended.

If a second short-term follow-up measurement result is greater than 200 Bq/m

3

, then

remedial action is recommended.

1.8 Measurements in Public Buildings

Buildings with a high occupancy of long duration by the public, such as hospitals, long-

term care residences, correctional facilities, schools and daycare centres are “public

buildings” and the Radon Guideline applies.

Buildings where the occupants are employees are “workplaces”, and the exposure to

radon is governed by the Canadian Guidelines for Management of Naturally Occurring

Radioactive Materials (NORM).

Measurements in public buildings provide a different set of challenges from dwellings.

Hospitals, long-term care residences and correctional facilities are occupied continually,

and so a long-term measurement will give a good estimate of the radon exposure of the

occupants. Schools and daycare centres are occupied only during the day, five days a

week, and so require specific guidance.

Health Canada recommends that the initial radon measurement in a public building be a

long-term measurement. If the result is greater than 200 Bq/m

3

, then remedial action is

recommended within the time frame suggested in the Guideline.

In some cases, however, a more rapid answer may be required to decide on the need for

further measurements. In these cases, short-term measurements lasting only a few days

may provide sufficient information. Wherever possible, these short-term measurements

should be made during the cold season (i.e. October to April) when radon levels are

generally the highest.

1.8.1 Measurement Location in Public Buildings

Public buildings differ from houses in that the occupants are not involved in the

measurement process. The choice of the measurement device location is constrained by

the need for security so that the devices are not readily accessible by curious occupants.

The buildings usually contain many rooms. (A room is the space enclosed by walls that

reach the ceiling. A room subdivided by partitions can be treated as one room.)

To provide a defensible radon concentration estimate for the building, measurements

should be made in the lowest-level occupied rooms of the building, preferably at the same

time. If there are more than 25 rooms, the additional measurements can be made at the

rate of one measurement per 200 m

2

floor area.

The device location should be selected so that there is a reasonable expectation that

it will not be disturbed during the measurement period.

• The preferred device location is by an interior wall at a height above the reach of

most people – 2.5 to 3 m from the floor.

• Measurements should not be made in bathrooms because relatively little time is

spent in a bathroom.

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• Measurements should not be made in closets, cupboards, sumps, crawl spaces, or

nooks within the foundation. Radon concentrations in these areas are not

representative of the concentration in the occupied area of the building.

• The device location should not be in air currents caused by heating, ventilating

and air conditioning vents, doors, fans and windows. Locations near heat, such as

over radiators, near fireplaces or in direct sunlight, should be avoided as some

measurement devices may be affected.

• Measurements during the warm weather in buildings without central air

conditioning are likely to give misleading results due to the very high likelihood

that windows will be open during the measurement period.

1.8.2 Interpretation of Measurement Results in Public Buildings

2.6.2.1 Long-term Measurements

If the result of a long-term measurement in part of a public building is greater than

200 Bq/m

3

, then remedial action is recommended for that part within the time frame

suggested in the Guideline.

2.6.2.2 Short-term Measurements

If the result of a short-term measurement in part of a public building is greater than

200 Bq/m

3

, a follow-up measurement with a long-term method is recommended. The

follow-up measurement should be made at the same location as the initial measurement.

If the result of a short-term measurement in part of a public building is greater than

600 Bq/m

3

, the follow-up measurement may be made with a short-term method. The

follow-up measurement should be made at the same location as the initial measurement.

If the result of a follow-up measurement in part of a public building is greater than 200

Bq/m

3

, then remedial action is recommended for that part within the time frame

suggested in the Guideline.

1.9 Measurements in Schools and Daycare Centres

Schools and daycare centres are occupied only during the day, five days a week, and the

heating and ventilation systems often operate differently when the school is not occupied.

As this may affect the radon concentration, a representative estimate of student exposure

requires measurements to be made only while the school is in session.

1.9.1 Measurement Location in Schools and Daycare Centres

To provide a defensible radon concentration estimate for the school, measurements

should be made in the lowest-level occupied classrooms of the building, preferably at the

same time. If there are more than 25 classrooms in this category, the additional

measurements can be made at the rate of one measurement per 200 m

2

floor area.

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The device location should be selected so that there is a reasonable expectation that

it will not be disturbed during the measurement period.

• The preferred device location is by an interior wall at a height above the reach of

most pupils – 2 to 3 m from the floor.

• Measurements should not be made in bathrooms, closets, cupboards, sumps, crawl

spaces, or nooks within the foundation. Radon concentrations in these areas are

not representative of the concentration in the occupied area of the building.

• The location should not be in air currents caused by heating, ventilating and air

conditioning vents, doors, fans and windows. Locations near heat, such as over

radiators, near fireplaces or in direct sunlight, should be avoided as some

measurement devices may be affected.

Because of the cyclic occupancy of the building, a short-term measurement of 2 to 5 days

during the cold weather months of October through April is suggested. The measurement

should take place during the five days while the school is in session.

The short-term measurements should be done with the HVAC system operating at normal

weekday settings, with the usual setback periods and with the building closed, except for

normal entry and exit, starting at least 12 hours before the beginning of the measurement.

To ensure valid results, it is important that doors and windows be kept closed except for

normal exit and entry. This minimizes the unpredictable impact on radon levels caused by

air currents and air pressure changes from outside weather conditions.

To ensure cooperation of teachers and staff in maintaining closed-building conditions, it

is recommended that the school principal talk to staff personally about the importance of

keeping doors and windows closed during the measurement.

Measurements that include weekends or holidays may not provide results that reflect the

exposure of pupils and teachers for the HVAC may operate differently on weekends,

repair work may be in progress, and so forth. All these conditions can affect radon levels.

Measurements during the warm weather, in buildings without central air conditioning, is

likely to give misleading results due to the very high likelihood that windows will be

open during the measurement period.

1.9.2 Follow-up Measurements

It is expected that follow-up measurements will be made in the rooms with the highest

measurements with an active continuous radon monitor that has the capability to integrate

and record a new result at least hourly. This will indicate if the measured radon

concentration is a realistic estimate of the concentration while the pupils are present.

1.9.3 Interpretation of School Measurement Results

If the result of these measurements in part of a school shows that the average radon

concentration while occupied is greater than 200 Bq/m

3

, then remedial action is

recommended for that part within the time frame suggested in the Guideline.

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Section 2: Measurements for Real-Estate Transactions

2.1 Introduction

In areas of known high radon concentrations in dwellings, potential buyers (and their

financiers) seek assurance that the dwelling has low radon concentrations, either naturally

or because remedial work has been carried out. These real-estate transactions are

expected to generate a significant proportion of radon measurements. As both buyer and

seller hope to proceed expeditiously, the time constraints present radon measurement

issues not encountered in the owner measurements discussed in Section 2.

These real-estate transaction protocols have been developed specifically to deal with the

time-sensitive nature of home purchases and sales. They are intended to provide buyers,

sellers, real-estate agents and measurement organizations with a common basis of

understanding of the procedures for radon measurements and interpretation of the results.

If the dwelling has been measured for radon according to the protocols in Section 2, in

advance of putting it on the market, the buyer may accept that result. However, many

buyers will request an independent radon measurement. (Some home inspection

companies may offer a radon measurement as part of a pre-purchase inspection package.)

As the owner may feel it advantageous that the measured radon concentrations in the

dwelling are low, the faith that the purchaser may have in the measurement is highly

dependent upon the assurance that the measurements are valid by methods to detect

interference with the measurement device or the house conditions, plus quality control

activities on the radon measurement devices.

2.1.1 Measurement Location for Real-Estate Transactions

Measurements made for a real-estate transaction should be performed in the lowest level

of the dwelling that is suitable for occupancy. This includes a lower level that is not

currently used, such as an unfinished basement that could be converted into a recreation

room, bedroom, or playroom.

In the absence of a basement, potential measurement locations include lower level family

rooms, living rooms, dens, playrooms, and bedrooms.

• A location should be selected where the device will not be disturbed during the

measurement period.

• Measurements should not be made in kitchens, laundry rooms, or bathrooms.

• Measurements should not be made in closets, cupboards, sumps, crawl spaces, or

nooks within the foundation. Radon concentrations in these areas are not

representative of the concentration in the occupied area of the house.

• The preferred device location is by an interior wall at least 50 cm from the floor

and at least 10 cm from other objects. The optimal height is in the breathing zone

– 0.8 to 2 metres from the floor.

• The location should not be in air currents caused by heating, ventilating and air

conditioning vents, doors, fans and windows. Locations near heat, such as over

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radiators, near fireplaces or in direct sunlight, should be avoided as some

measurement devices may be affected.

In the case of newly constructed and unoccupied dwellings, the radon measurement

should be carried out after the following have been installed:

• all insulation,

• all exterior doors and hardware,

• all windows,

• fireplaces and fireplace dampers,

• all heating/cooling appliances (functioning and set to run at normal occupied

temperatures),

• all ceiling coverings,

• all interior trim and coverings for exterior walls,

• all exterior siding, weatherproofing and caulking.

Structural openings to the exterior as a result of incomplete construction, structural

defect, disrepair, or the like must be closed or repaired 12 hours prior to initiating a short-

term measurement.

2.2 Options for Real-Estate Measurements

Based on US experience, two short-term measurement options are satisfactory and are

described here. The availability of two options allows flexibility for the party carrying out

the measurement. Each of these options will produce results that can be used to determine

the need for remedial action.

2.2.1 Option 1: Passive Device Measurement

This option involves the use of two simultaneous 48 hour short-term measurements

conducted with the same type of device placed side-by-side (<10 cm apart). The

measurements are carried out under closed-building conditions as described in Section 2.

If a radon reduction system is in place, make sure the system is in operation during the

entire radon measurement. The same type of measurement device should be used for each

measurement. Using different devices for the two measurements may increase the

potential for differences between the two results.

2.2.1.1 Interpretation of Passive Device Measurement Results

Because radon measurements, like any measurements, usually do not produce identical

results, there will usually be a difference between the two results. So that clients may

have confidence in the results:

• If the higher result is twice or more than the lower result, then a re-measurement

should be conducted.

• If the higher result is between 1.5 to 2 times greater than the lower result, a

re-measurement is not necessary, but the source of the variability should be

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investigated. The results of both measurements and the average of the two results

should be reported to the client.

Both measurement results and the average result should be reported to the client. The

results of the simultaneous measurements will fall into one of the two categories

discussed below:

• Average of the two measurements is less than 200 Bq/m

3

- remedial action is not

necessary.

• Average of the two measurements is more than 200 Bq/m

3

- remedial action is

recommended within the time frame suggested in the Guideline.

2.2.2 Option 2: Active Device Measurement

This option requires an active continuous radon monitor that has the capability to

integrate and record a new result hourly. The measurement is carried out under closed-

building conditions as described in Section 2. If a radon reduction system is in place,

make sure the system is in operation during the entire radon measurement. The minimum

measurement period is 48 hours.

The first four hours of data from the continuous monitor may be discarded to allow for

the monitor coming to equilibrium with its surroundings. There must be at least 44

consecutive hours of usable data to produce a valid average. The hourly results are

averaged to produce the result that is reported to the client.

The approaches to increase the confidence in results obtained with active monitor devices

include the use of device self-diagnostic features and data validation or verification

procedures, such as check sources before and after each measurement, and use of

spectrum readouts. Other features include (but are not limited to) the ability to check

airflow rates and voltages before and after each measurement. Measurement companies

should incorporate such checks into their routine instrument performance checks as part

of their standard operating procedures.

Additional features that can increase confidence in measurement results are those that

detect measurement interference; these features are discussed in Section 2.2.3

Measurement Interference. For example, a device that offers a variety of ways to detect

tampering may deter, as well as detect, interference with the device's operation or proper

closed-building measurement conditions. Potential tampering indicators include the

ability of a device to record changes in temperature, humidity, or movement of or around

the device during the measurement.

The reliability of any type of equipment, however, needs to be established and

documented via a complete quality assurance program. This includes routine instrument

performance checks prior to and after each measurement, annual calibrations, semi-

annual instrument cross-checks, and frequent background and spiked measurements.

2.2.2.1 Interpretation of Active Device Measurement Results

Both the hour-by-hour measurement results and the average result over the effective

measurement period should be reported to the client.

If the average is less than 200 Bq/m

3

- remedial action is not necessary.

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If the average is more than 200 Bq/m

3

- remedial action is recommended within the time

frame suggested in the Guideline.

2.2.3 Measurement Interference

The owner of a dwelling may have an interest in the measurement results being low to

avoid hindering the sale of the dwelling, or incurring the added expense of having to

install a mitigation system. The potential for measurement interference puts the

professional radon measurer into the position of verifying that the equipment and the

required measurement conditions have been maintained. A measurement result below the

action guideline may be suspect if the measurer cannot verify that the necessary

measurement conditions were maintained.

Interference with a radon measurement is defined as the altering of measurement

conditions prior to or during the measurement to either change the radon or decay product

concentrations in the measurement area, or to alter the performance of the measurement

equipment with the intent of producing a low result. The following discussion reviews

some of the types of measurement interferences and methods of detecting and preventing

such interferences.

2.2.3.1 Influencing Measurement Area Concentration

The primary method of temporarily reducing radon levels is to ventilate the measurement

area with outdoor air. Ventilation will slow down radon entry by reducing negative

pressure in the measurement area and by diluting the radon concentration. Even small

openings of a single window in the measurement area can have a large effect. Ventilating

the floors above the measurement area has significantly less effect, unless the

measurement area is connected with the ventilated room by an operating central air

handling system.

2.2.3.2 Equipment Interference

The primary method of interfering with measurement equipment is to move the device to

an area of low radon concentration. However, interfering with air sampling mechanisms

of active monitors can maintain the radon concentration at the time of interference, or

cause a large decrease in the reported concentration.

A passive detector could be turned off or sealed in its radon-proof transport container

during most of its exposure period. Just covering a passive detector could cause the

reported values to be much less than the true value. In addition, some passive detectors

will read low under conditions of high heat or humidity.

2.2.4 Preventing Interference

Radon measurements conducted for a real-estate transaction must be performed using

tamper-resistant measurement techniques. It is more advantageous for the measurer to

take steps to prevent interference rather than to simply detect it.

Preventing interference can best be accomplished by:

• Educating the parties to a real-estate transaction about the necessary measurement

conditions.

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• Including in standard documentation for each measurement an agreement signed

by the parties involved in the real-estate transaction listing the necessary

measurement conditions and their agreement not to interfere with the conditions.

• The agreement should also state that the measurer may nullify the measurement

results at their discretion if they believe the devices were interfered with.

• Informing the client that interference with the measurement conditions may

increase the radon levels.

• Informing the client that interference-detecting techniques are in use and allow the

documentation of the interference with a measurement.

Common equipment and techniques for detecting measurement interference and

tampering are listed below:

• The ability to integrate and record radon measurements over intervals of an hour

or less is an important tamper-detection feature. These monitors can indicate

unusual concentration changes that can be indicators of measurement interference.

• Measuring other parameters that may provide additional indicators of equipment

interference, such as a detector tilt or motion indicator, or a continuous recording

of pump flow rate. Cages for passive monitors can be equipped with a movement

indicator to deter handling.

• Measurement of CO2 levels can indicate changes in the measurement area

infiltration rate of outdoor air.

• Temperature and humidity readings may indicate changes in the infiltration rate of

outdoor air.

• Instruments that do not allow occupants to view preliminary results (via a visible

printer or screen) may reduce the incentive for interference.

Seals can aid in detecting and discouraging measurement interference and are especially

important in the absence of other tamper-detection. It is advisable to use seals

manufactured specifically for radon measurement and follow the manufacturer's

installation instructions.

Seals can be placed between the detector and its support to verify that detectors have not

been moved, or the detector has not been opened.

Seals should be placed on the lowest operable windows and non-primary exterior doors.

A seal may be placed on the furnace control fan switch and on the thermostat.

Upon retrieval of the detector, the measurer should carefully inspect and record the

following:

• Closed-building conditions are still being maintained;

• Changes in the detector placement;

• The condition of all seals; and

• Any abnormal variations in any of the measurements made.

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Section 3: General Procedural Recommendations

This section outlines basic procedural recommendations for real-estate and non real-

estate related radon measurements in homes.

3.1 Real-Estate Measurements

Section 3 provides protocols for real-estate measurements.

3.1.1 Initial Client Interview

Reasonable efforts should be made to determine whether the home is new or occupied,

and who will be in charge of the home during the measurement period. Organizations that

provide measurement services, or place or retrieve devices, should review the protocol

options and the clients’ needs, and inform clients of the buildings and measurement

conditions necessary for conducting valid measurements. These organizations should use

only those devices or methods for which they are proficient.

Measurement organizations should inform the client and other parties of the real-estate

transaction of:

• The appropriate measurement recommendations as outlined in this document.

• The types of devices they will be using for the measurement.

• A statement of whether the device measures radon or radon decay products.

The results of radon decay product measurements should be reported in working

levels (WL). The WL value should be converted to an equivalent radon

concentration in the unit of Bq/m

3

for comparison with the Radon Guideline using

a 50% equilibrium ratio (unless the device measures the actual equilibrium ratio).

• Specific information on the minimum and maximum duration of exposure for the

device.

• A description of closed-building conditions and a stated requirement that these

conditions must be maintained 12 hours prior to and during all short-term

measurements.

• Directions that the building's heating, ventilating, and air conditioning (HVAC)

system and any existing mitigation system should be normally operated 24 hours

prior to and during all measurements.

• A permanent radon reduction system should be fully operational for at least 24

hours prior to measurement to determine the mitigation system's effectiveness.

The mitigation system is to be operated normally and continuously during the

entire measurement.

• A written non-interference agreement, to be signed and returned by the occupants,

confirming that they followed all instructions and did not interfere with the

measurement device or building conditions.

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3.1.2 Conditions for a Valid Measurement

Measurements should not be conducted if temporary radon reduction measures have been

implemented. These include the introduction of unconditioned air into the home or

closure of normally accessible areas of the home. In this case, the measurement

organization should inform the client and other parties of the real-estate transaction that

these conditions have been corrected.

If the measurer arrives at a property and finds windows or doors open, or suspects that

closed-building conditions were not maintained for 12 hours prior to arrival, then the

measurer should extend the measurement to account for this condition.

3.1.3 Anti-Interference Documentation

Measurement organizations should, in addition to providing written guidance, take steps

to identify attempts to interfere with the measurement device or building conditions.

The signed non-interference agreement, a description of all non-interference controls

employed, and a statement addressing any observed breaches of the non-interference

agreement/controls should be made part of the permanent measurement documentation

for each measurement.

3.2 Measurements by Clients

Measurement devices installed by the client must be accompanied by instructions for

placing, retrieving and handling the device. These instructions should include specific

information on the minimum and maximum length of time that the device must be

exposed.

For short-term measurements, instructions on closed-building conditions must be

included.

Documentation should be substantially the same as for real-estate measurements. The

anti-interference agreement can be omitted.

3.3 Documentation

Measurement organizations should record sufficient information on each measurement in

a permanent log to allow for future data comparisons, interpretations and reporting to

clients.

Health Canada maintains a geographic database of radon measurements. The results of

each measurement, the detector type, the start and finish dates and the postal code of the

building should be forwarded to the Health Canada for each month that measurements are

made.

3.3.1 Measurement Log

It is suggested that a measurement log be kept and maintained for five years with the

following information:

• A copy of the final report, including the measurement results, and the statement

outlining any recommendations concerning re-measurement or mitigation that

was provided to the building occupant or agent.

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• The address and postal code of the building measured.

• The locations of all measurement devices deployed. It is advisable to diagram the

measurement area, noting the exact location of the detector.

• Start and stop times, and dates of the measurement period.

• A description of the device used, including its serial number if any.

• The name of the organization conducting the analysis.

• A description of any vents used in crawl spaces or in supplying air to combustive

appliances.

• The name of the individual who conducted the measurement.

• A description of any variations from, or uncertainties about, standard

measurement procedures, closed-building conditions or other factors that may

affect the measurement result.

• A description of any non-interference controls used and copies of signed non-

interference agreements.

• A record of any quality control procedures associated with the measurement, such

as results of simultaneous or secondary measurements.

3.4 Quality Assurance in Radon Measurements

3.4.1 Quality Assurance Plans

All measurement organizations should develop, implement, revise periodically, and

maintain a detailed quality assurance plan (QAP) appropriate to each device or method

used. These plans should include written procedures for attaining quality assurance

objectives, and a system for recording and monitoring the results of the quality assurance

measurements described below.

Organizations that only use radon measurement devices analyzed by third parties still

need to write and follow a QAP, and conduct quality control measurements.

3.4.2 Standard Operating Procedures

Organizations should have a written, device-specific standard operating procedure (SOP)

in place for each radon measurement system they use. An SOP must include specific

information describing how to operate and/or analyze a particular measurement device.

Organizations that analyze devices should develop their own SOP or adapt manufacturer-

developed SOPs for their devices. Organizations that receive results from a laboratory

should have a device-specific SOP for each brand/model/type of device they use.

3.4.3 Calibration Measurements

Calibration measurements are made in a known radon environment such as a calibration

chamber to determine and verify the conversion factors used to derive the concentration

results. Determination of these calibration factors is a necessary part of the analysis and is

the responsibility of the analytical laboratory.

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These calibration measurement procedures, including the frequency of measurements and

the number of devices to be measured, are specified in the quality assurance programs

operated by the device manufacturers and analysis laboratories. This data should be

available to the device users for use in their quality assurance program.

Measurement providers are required to recalibrate active devices at least once every 12

months.

3.4.4 Known Exposure Measurements

Analysis laboratories for passive radon measurement devices should provide for the

introduction of controls (devices exposed to known concentrations in a radon calibration

chamber) into their measurement processes. Control devices should be labelled and

submitted to the laboratory in the same manner as ordinary samples. The results of these

measurements are used by quality assurance programs to monit