How to read an indoor air quality report (and what to do with it)

An indoor air quality (IAQ) assessment produces a lot of numbers. Without a reading grid, it ends up in a drawer. Here is how our engineers read one, and above all what they deduce for your installations.

1. CO₂: the witness of air renewal

Carbon dioxide is not a pollutant in itself at the concentrations found in a building: it is an indicator of confinement. A concentration that climbs through the day in an occupied room means the fresh-air flow is not keeping up with actual occupancy.

1. A stable plateau close to outdoor levels: ventilation is doing its job.
2. A continuous rise across the day: insufficient flow, an obstructed diffuser or an unbalanced network.
3. Peaks at every meeting: the control system is not responding to occupancy.

2. Fine particles: find the source before you filter

PM2.5 and PM10 tell two different stories. Levels correlated with outdoor air point to the air handling unit’s filtration; indoor levels higher than outdoors point to a source inside the building: a process, a kitchen, works in progress, or a fouled duct network shedding deposits.

3. VOCs and humidity: the slow signals

Volatile organic compounds often appear after a fit-out (furniture, coverings) or reveal ventilation too weak to evacuate everyday emissions. Relative humidity is read over time: above a certain threshold for several days, it prepares the ground for mould in ducts and ceiling voids.

4. From the report to an action plan

1. Cross the readings with occupancy. A number without its time context says nothing.
2. Check the network before touching the setpoints. A camera inspection often shows that the theoretical flow never reaches the diffuser.
3. Prioritise. Rebalancing, filter replacement, duct cleaning: each action has a cost and a measurable effect. Run a follow-up campaign after the work.

A good IAQ report ends with ranked recommendations, not a table. If yours doesn’t, that is the first thing to ask for.