Testing The Air
Most air quality questions in a Toronto house are answered by a hygrometer and a careful look rather than by a laboratory.
Short answer
Testing is useful for specific questions with an action attached: radon, carbon monoxide, and in some cases mould spores or formaldehyde. A general "air quality test" offered with a duct cleaning quote is a sales tool. Start with humidity, ventilation and visible sources, which account for most complaints.
Worth testing for
Radon, which is a genuine issue in parts of Ontario and which can only be established by a long-term test. Health Canada recommends testing and publishes a guideline level.
Carbon monoxide, continuously, with an alarm rather than a one-off test — which is required in Ontario homes with fuel-burning appliances.
Mould, where there is a specific question — a dispute, a disclosure, a medical referral — rather than as a general check.
Formaldehyde and volatile compounds after a renovation or new furniture, where symptoms have followed a known event.
Asbestos, where material is going to be disturbed in an older house, which is a bulk sample rather than an air test.
And lead, in the same circumstances.
Radon is the one to do
Of everything on this list, radon is the test most Toronto homeowners should actually do and almost none have. It needs a long-term test during the heating season rather than a short one, the kits are inexpensive, and if the level is high the mitigation is a known and affordable piece of work.
What to check before testing anything
Indoor humidity with a hygrometer, in two or three rooms. Most winter complaints in a Toronto house are a humidity number.
Whether the HRV is running and whether its filters are clean.
Whether the bathroom and kitchen fans work and actually exhaust outside.
Whether the furnace filter is the right size and seated, and whether the filter slot is sealed.
Whether there is visible mould anywhere, which answers the question without a test.
And whether the return side is drawing from a damp basement or crawlspace, which is a smell test rather than a laboratory one.
Why general air testing disappoints
There is no single meaningful number for air quality, so a report with one is not telling you much.
Spore counts vary enormously with time of day, activity and whether a window was open.
There is no published safe level for indoor spore counts, so the comparison is with a sample taken outdoors on the same visit.
A test that cannot change what you do is a receipt rather than information.
A test offered by the company quoting the remediation is a conflict worth avoiding.
And a visible problem does not need confirming; it needs fixing.
Common questions
Should I test my indoor air?
Test for radon. Have a carbon monoxide alarm. Beyond that, test for specific questions only.
What should I check first?
Humidity with a hygrometer, and whether the ventilation actually works.
Is a general air quality test useful?
Rarely. There is no single meaningful number and the results vary enormously.