Buying indoor air quality testing services: why professional indoor air quality testing starts with a walkthrough and a question rather than a sampling pump, which parameters are worth measuring first, and how to read a result that has no legal limit attached to it

Commissioning it in the right order

1. Start with the complaint and a walkthrough. Who is affected, where, when and since what change. A competent investigator walks the space, looks at the ventilation system and the moisture history, and forms a hypothesis before any sampling. Sampling without one is expensive guessing.
2. Measure carbon dioxide as a ventilation proxy first. It is cheap, continuous and it answers the commonest underlying question, which is whether the space is ventilated for its occupancy. Concentrations tracking occupancy and staying high indicate under-ventilation, and that explains a great many complaints on its own.
3. Add temperature, humidity and particulate measurement. Comfort parameters explain more complaints than contaminants do, and relative humidity drives both mould risk when high and irritation when low. Particulate measurement identifies combustion and outdoor ingress.
4. Sample for specific contaminants only against a hypothesis. Volatile organic compounds, formaldehyde, mould or carbon monoxide are targeted tests. Which method, over what duration, and where the sample is taken all follow from what you suspect, and a laboratory needs that to quote sensibly.
5. Fix the reference you will read the result against before you get it. Most indoor parameters have guidance values rather than legal limits, and occupational exposure limits are set for an industrial workforce rather than an office. Agree what a result will be compared against before it arrives, or it cannot be acted on.

The outdoor comparison that makes a result interpretable

For particulates, mould spores and many volatile compounds, the indoor number means little without a simultaneous outdoor measurement. An indoor concentration below outdoor is a very different finding from the same number with clean air outside.

Take the outdoor sample at the same time with the same method. A comparison against a published average for the region is not the same measurement and will be challenged.

Who to commission

An investigator who will walk the building and write a hypothesis, using an accredited laboratory for any analysis. A provider who quotes a fixed panel without seeing the space is selling a panel rather than an investigation.

Check the analytical laboratory's scope of accreditation covers the specific methods, and ask whether the sampling is performed to a recognised method or to the provider's own procedure.

Acting on the result

Most findings lead to ventilation adjustment, a moisture repair or removing a source, and all three are building work rather than further testing. A report that ends in a recommendation to test more has usually not found the problem.

Re-measure after the remedy, with the same method in the same positions. Without a post-remedy measurement there is no evidence the work achieved anything, and the complaint frequently returns.

Common questions

What should indoor air quality testing services measure first?

Carbon dioxide, temperature, relative humidity and particulates, continuously and during occupancy. These are cheap, they identify the ventilation and comfort problems behind most complaints, and they tell you whether targeted contaminant sampling is even warranted.

Are there legal limits for office air quality?

Generally no, in the way people expect. Occupational exposure limits exist for workplaces with specific hazards and are set for an industrial context; office guidance values are advisory. Agree the comparison basis before commissioning the work.

Should I test for mould?

Only against a hypothesis. Air sampling for mould is difficult to interpret without an outdoor comparison and without knowing what normal is for that building. A moisture survey and a visual inspection usually answer the question better and cost less.

How long should sampling run?

Long enough to cover occupied and unoccupied periods, which usually means days rather than a single spot reading. A single reading at a quiet moment is the classic way to miss the problem entirely.

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