Indoor Air Quality Checklist

The order of this document is its argument: complaints first, instruments second. An air quality survey carried out the other way round is a measurement exercise looking for somewhere to happen, and it reliably produces a clean sheet. The surveyor arrives in the morning because that is when access is easy, measures in a meeting room because it is empty and convenient, finds carbon dioxide and everything else comfortably within guideline, and reports that the air is fine. Every one of those readings is accurate and the report is worthless, because the complaints came from an open plan floor at half past two with the floor full, and nothing was measured there at that time. Mapping the complaints first fixes this almost entirely: a pattern by location and by hour tells you which rooms matter and when to be in them, and it frequently diagnoses the problem before an instrument is switched on. Afternoons on one floor only, worsening through the week, is a ventilation rate problem. Everywhere at once, starting three weeks ago, is something that changed. One corner, all day, is a source. The second thing worth copying is the field that asks whether the outside air dampers have been closed down, which gets its own line because it is both the commonest cause and the most understandable one. Fresh air is expensive to heat and to cool, closing the dampers reduces that cost immediately and visibly, and the consequences appear weeks later as tiredness, headaches and stuffiness that nobody connects back to an energy-saving measure taken in a plant room by somebody who no longer works here.

At 1,240 parts per million the reading is not dangerous and it is not the point; it is the cheapest available evidence that not enough fresh air is reaching the people on that floor. Carbon dioxide at normal office levels harms nobody directly. What it does is track almost perfectly with ventilation rate per person, which means a reading well above guideline on an occupied floor is a measurement of under-ventilation that can be taken in ten minutes with one instrument, and under-ventilation is what produces the stuffiness, drowsiness and headaches that six of the eight complaints described. That is why the likely cause and the action both point at a damper rather than at a filter or a diagnosis. The second number is the one that stops this being a clean sheet. Nine of twelve parameters within guideline reads well, and six of eight complaints explained says something much more useful: two complaints still describe a problem that nothing measured accounts for. That is not a failure of the survey so much as its most honest output, because it says where to go back and what to look for, whereas a report claiming everything is fine while people continue to complain generates more complaints rather than fewer. The condition of the plant moving this air is a separate survey with separate instruments, the ventilation inspection checklist, and the two read best together.

These two surveys are complementary to the point that either one alone is quite likely to mislead you. An air quality survey finds that a floor is under-ventilated at two in the afternoon and cannot tell you why: the fresh air rate is low, and that could be a damper, a fouled coil, a leaking duct, a filter at the end of its life, a terminal somebody closed or a system that was never balanced after a refit. It measures the symptom accurately and stops there. A ventilation inspection finds the mechanical cause precisely, terminal by terminal and damper by damper, and has nothing whatever to say about whether the people on that floor are comfortable, because it is carried out in plant rooms and ceiling voids, usually when the building is empty and access is easy. Run on their own, the first produces a finding nobody can act on and the second produces a maintenance report nobody reads. Run together, the air survey says which floor and which hour, the ventilation inspection says which terminal and by how much, and the action that follows is specific. This page deliberately limits its ventilation section to the nine things that affect the air directly, filter grade and bypass, coil and tray cleanliness, heat recovery cross-contamination and extract ducted outside, and leaves the condition of the plant to the ventilation inspection checklist and the servicing of it to the HVAC maintenance checklist.