How often should indoor air quality be monitored in commercial buildings?

There isn’t a single rule that fits every building, but as a general guide, indoor air quality (IAQ) in commercial buildings should be reviewed at least annually. This works well for offices with stable occupancy, good ventilation, and no recent issues. However, buildings that rely heavily on mechanical ventilation, house sensitive activities, or have a history of complaints may need more frequent checks.

In many cases, I recommend a baseline assessment, followed by periodic monitoring or continuous sensors for key parameters like carbon dioxide (CO2), temperature, and humidity. CO2 is often used as an indicator of ventilation effectiveness, rather than a pollutant on its own.

Monitoring should also be triggered by change. That could include refurbishments, changes in occupancy, new equipment, or recurring complaints such as headaches, fatigue, or odours. Seasonal changes can matter too — winter heating and reduced fresh air intake often reveal issues that weren’t obvious in summer.

Ultimately, the right frequency depends on risk. Higher-risk environments benefit from ongoing oversight rather than a one-off snapshot, which can miss developing problems.