Five Days, Five Checks: A Facilities Team's Working Week of Air Quality Diagnostics
Photo: U.S. Air Force photo by Senior Airman Rome Bowermaster, Public domain, via Wikimedia Commons
Walk into almost any commercial building in Britain and ask the facilities manager how the air quality is performing, and you will usually receive one of two answers: a shrug, or a reference to the last service visit. Neither is really an answer. Air quality is a measurable, manageable asset — yet because it is invisible, it tends to be managed on faith rather than evidence.
It does not have to be that way. Before commissioning a full indoor air quality assessment, there is a great deal your own team can establish with a diary, a few pounds of equipment and one working week. Here is how to structure it.
Monday: The Paper Trail
Begin not with instruments but with paperwork. Pull together the most recent service records, filter change logs and any F-Gas or TR19 documentation. Look for three things: intervals that have slipped, filters replaced on a calendar basis rather than a condition basis, and any recurring notes about airflow imbalance or blocked terminals.
If the last filter change was logged but nobody can say what condition the old filter was in, your ventilation system has been running blind. That single observation shapes the rest of the week.
Tuesday: The Smoke Test
For under a tenner, a stick of incense is one of the most informative diagnostic tools in the building. Held near air intake grilles, doorways and high-occupancy corners, the smoke reveals what instruments cannot: which way the air is actually moving.
Watch for smoke drifting out of a room rather than into it, which suggests negative pressure and possible back-draughts from adjoining spaces — including WCs, kitchens and plant rooms. Smoke that stalls and swirls in the middle of an office indicates dead zones where neither supply nor extract is doing its job. Photograph everything; patterns across multiple rooms tell a story.
Wednesday: The CO2 Watch
Invest in a non-dispersive infrared CO2 monitor — reputable models are available for £60–£150. Place it in your most densely occupied space at breathing height, away from windows and doors, and log readings through a normal working day.
As a rule of thumb: sustained readings above 1,000 ppm indicate under-ventilation; above 1,500 ppm, occupants will report drowsiness and reduced concentration; above 2,000 ppm, the space is failing its occupants outright. Given that fresh-air ventilation rates in offices are now a genuine recruitment and retention concern, a Wednesday of readings gives you a baseline you can act on — and demonstrate compliance against BS 40102 expectations.
Thursday: The Dust Audit
Sticky tape is not a laboratory instrument, but it is honest. Press a strip of clear tape onto supply diffusers, high shelving and the tops of partition walls, then examine it against a white sheet of paper.
Grey, fibrous deposits suggest filter bypass or degraded filtration. Greasy, tacky films point to kitchen extract or nearby road traffic ingress — common in city-centre buildings near bus routes. Black speckling near grilles can indicate mould, which warrants immediate professional investigation rather than a wipe-down.
Friday: The Occupancy Interview
Finally, ask the people. A five-question survey — headaches by mid-afternoon? stuffiness near the windows? odours from neighbouring units? temperature swings? symptom relief on leaving the building? — costs nothing and frequently surfaces patterns the instruments corroborate. Cross-reference complaints with Tuesday's smoke tests and Wednesday's CO2 log.
Interpreting the Results
If your week produced clean smoke movement, CO2 readings consistently below 1,000 ppm and minimal dust deposition, your building is in reasonable health and your maintenance regime is probably sound. Book routine servicing and revisit the audit in six months.
If, however, you found dead zones, sustained high CO2, visible deposits or clustering complaints, you now hold something valuable: evidence. A professional assessment with proper instrumentation — airflow measurements, filtration analysis, humidity and temperature mapping — can be targeted precisely rather than commissioned on guesswork, which usually reduces the overall cost.
From Mystery to Management
The point of the exercise is not to replace professional expertise — some things genuinely require calibrated instruments and qualified engineers. It is to replace assumption with data. A facilities team that can say "our Wednesday boardroom reads 1,400 ppm by 11am" is in a categorically stronger position than one that says "the air feels a bit stuffy."
Run the audit once a quarter, keep the logs, and air quality stops being an invisible mystery and becomes what it should be: a managed asset with numbers attached. And when the numbers say it is time, bring in the specialists — with a week of your own evidence to show them.
