Where to Place a Radon Detector for Accurate Results

If you have a basement:

• •Test the basement if you use it regularly (daily or weekly)
• •Examples of regular use:

If basement is rarely used:

• •Test the first floor (ground level) instead
• •Basement storage that you visit monthly doesn't count as "lived-in"

If you have no basement:

• •Test the first floor (ground level)
• •This is where radon accumulation is typically highest

Multi-level considerations:

• •Start with lowest lived-in level
• •If that test shows elevated levels, consider testing other levels too
• •Upper floors typically have lower radon levels, but not always

Why the lowest level:

• •Radon enters primarily from soil through foundation
• •Highest concentrations typically found at lowest levels
• •Testing here gives worst-case scenario
• •Protects against maximum exposure

Definitely lived-in:

• •Spend 4+ hours per day in the space
• •Sleep in the space regularly
• •Work in the space daily
• •Use for primary activities (eating, entertaining, relaxing)

Probably lived-in:

• •Spend 1-3 hours daily in the space
• •Use several times per week
• •Children play there regularly

Not lived-in:

• •Visit less than weekly
• •Use only for storage
• •Pass through without stopping
• •Unfinished, unused areas

✅ Test these basement spaces:

• •Finished basement with bedroom
• •Home office where you work daily
• •Basement family room with TV
• •Playroom kids use daily

❌ Don't test these basement spaces:

• •Storage room visited monthly
• •Mechanical room (furnace area)
• •Unfinished areas not used for living
• •Workshop visited only occasionally

Initial testing:

• •Start with lowest lived-in level
• •This provides most conservative (protective) result

If initial test is high:

• •Consider testing other occupied levels
• •Helps understand radon distribution
• •Important if different family members use different levels

If initial test is low:

• •May still want to test levels you occupy most
• •Example: If basement is low but you sleep on first floor, test first floor too

Cost-benefit approach:

• •Most important: Test where you spend most time
• •Secondary: Test other occupied levels for complete picture
• •Each test costs $15-50, which is reasonable for peace of mind

Regularly occupied:

• •Living room
• •Bedroom (especially if basement bedroom)
• •Den or study
• •Home office
• •Playroom
• •Family room

Characteristics of good test rooms:

• •Used daily or near-daily
• •People spend extended time there (1+ hours)
• •Representative of how family uses the space
• •Has minimal air movement from outside
• •Not subject to extreme temperature changes

Priority rooms:

• •Bedrooms (you spend 8 hours/day sleeping)
• •Home offices (you spend 8+ hours/day working)
• •Living areas where family gathers

If choosing between multiple rooms:

• •Pick the room used most often
• •Or test multiple rooms (relatively inexpensive)
• •Bedrooms on tested level are particularly important

Kitchens:

• •High humidity from cooking
• •Frequent air movement from exhaust fans
• •Temperature fluctuations
• •Can affect detector accuracy

Bathrooms:

• •Very high humidity from showers/baths
• •Exhaust fans create air movement
• •Extreme humidity can damage some detectors
• •Not representative of long-term exposure

Laundry rooms:

• •High humidity from washer/dryer
• •Dryer vents bring in outside air
• •Temperature variations
• •Frequent door opening

Utility/mechanical rooms:

• •Furnace, water heater create air currents
• •Not lived-in spaces
• •May have unusual air pressure
• •Temperature extremes

Hallways:

• •High traffic creates air movement
• •Not representative of occupied space
• •Doors opening/closing affects readings

Closets:

• •Isolated from living space
• •May have unusual air circulation
• •Not where people spend time

Garages:

• •Attached garages have different air exchange
• •Detached garages not relevant to home
• •Not lived-in space

Why this range:

• •Breathing zone for adults and children
• •Where you actually inhale air
• •Avoids floor-level disturbances
• •Representative of human exposure

Recommended heights:

• •20-30 inches (50-75 cm): Good for general testing
• •30-40 inches (75-100 cm): Typical table or desk height (ideal)
• •40-60 inches (100-150 cm): Acceptable, breathing height when standing

Where to place within this range:

• •On a table or desk: Excellent
• •On a shelf: Good if stable
• •On a piece of furniture: Good if won't be moved

Avoid:

• •On the floor (not breathing zone, disturbed by walking)
• •Above 60 inches / 150 cm (not typical breathing height)
• •Ceiling level (not where you breathe)
• •On windowsills (affected by drafts)

Exterior walls:

• •Minimum 3 feet (1 meter) from exterior walls
• •Exterior walls affected by outdoor temperature
• •Can have unusual air currents
• •Not representative of room interior

Windows:

• •Minimum 3 feet (1 meter) from any window
• •Even closed windows create drafts
• •Air temperature differences affect readings
• •Sunlight can affect some detectors

Doors:

• •Minimum 3 feet (1 meter) from exterior doors
• •Door opening/closing creates air movement
• •Drafts affect accuracy

Heat sources:

• •Minimum 3 feet (1 meter) from:

Humid areas:

• •Minimum 3 feet (1 meter) from:

Air movement:

• •Minimum 3 feet (1 meter) from:

Ideal location:

• •Interior area of room
• •Away from all walls (middle of room is best)
• •On stable surface (table, shelf, desk)
• •Out of direct sunlight
• •Away from heat and humidity sources
• •Where it won't be disturbed

Stable placement:

• •On flat, level surface
• •Not on wobbly furniture
• •Not where pets can reach it
• •Not where children might play with it
• •Not in high-traffic areas where it might be bumped

Avoid vibration:

• •Not on washing machine or dryer (even if off)
• •Not on speaker or subwoofer
• •Not on floor in high-traffic area
• •Not on door or wall that vibrates

Visual reminders:

• •Place visible note near detector: "Radon Test - Do Not Disturb"
• •Inform all household members
• •Keep pets away from testing area

Protection from damage:

• •Not where items might be stacked on it
• •Not where it might get wet
• •Not where temperature extremes occur
• •Not in direct airflow from vents

If different levels have different foundations:

• •Test the level with the lowest foundation (deepest in ground)
• •This is typically where radon entry is greatest

If split level has basement on one side:

• •Test the basement if it's regularly occupied
• •Otherwise test the lower of the two main levels

Multiple tests recommended:

• •Test both major living levels if both are heavily used
• •Helps understand radon distribution in split-level design

Instead:

• •Test the first floor directly above crawlspace
• •This is where you actually live
• •Crawlspace levels don't directly indicate living space exposure

Detector placement:

• •First floor, away from floor vents/openings
• •In regularly occupied room
• •Follow standard placement guidelines

Test the first floor:

• •This is the lowest (and only) level
• •Follow standard room selection and placement rules

No basement or crawlspace:

• •First floor is the priority testing location
• •Radon enters through cracks in slab

Each unit is unique:

• •Test your individual unit
• •Neighbor's results don't predict yours
• •Radon varies unit to unit even in same building

Which level in your unit:

• •Lowest level you occupy regularly
• •If multi-story unit, test level where you spend most time

Special considerations:

• •Shared walls, floors, ceilings can affect radon
• •HVAC systems may be shared or individual
• •Test is still valid and necessary

Coordination:

• •May need building management permission
• •Some buildings have radon testing programs
• •Consider encouraging other residents to test

Finished basement (walls, ceiling, flooring complete):

• •Test in regularly used finished room
• •Follow standard placement guidelines
• •Treat like any other living space

Partially finished basement:

• •Test in the finished portion you use regularly
• •Don't test in unfinished storage areas

Unfinished basement you use regularly:

• •Still test if you spend significant time there
• •Examples: Workshop, exercise area, laundry you use daily
• •Place detector in area you use most

Unfinished basement rarely used:

• •Test first floor instead
• •Basement isn't "lived-in" if only for storage

Heating season (fall/winter) typically shows highest levels:

• •Windows and doors closed more often
• •Heating systems create more indoor-outdoor pressure difference
• •Less natural ventilation
• •More conservative (protective) test results

Cooling season (summer) typically shows lower levels:

• •Windows may be open more
• •Air conditioning affects air pressure
• •More air exchange with outdoors
• •May underestimate year-round average

Recommendation:

• •Short-term tests: Conduct during heating season for most conservative results
• •Long-term tests: Include both heating and cooling seasons for true annual average
• •If testing in summer, levels may be lower than annual average

Do not conduct 2-3 day short-term tests during:

• •Severe storms
• •Periods of unusually high winds
• •Extreme weather events

Why:

• •Unusual barometric pressure affects radon entry
• •High winds create abnormal air pressure
• •Results won't reflect typical conditions

If severe weather occurs during test:

• •Note it on test documentation
• •Consider retesting during normal conditions
• •Results may not be representative

Long-term tests (90+ days):

• •Less affected by temporary weather
• •Averaging over time provides more stable results