Indoor Air Quality Testing Instruments Guide

Why IAQ Now Sits Beside Energy

Post-pandemic, building owners are asked to prove ventilation works. Indoor air quality instruments have moved from research labs into routine commissioning kits. Five parameters cover most of what regulators and tenants want to see.

1. Carbon Dioxide (CO₂)

The cheapest and most useful proxy for ventilation rate. Outdoor air is ~ 420 ppm; ASHRAE 62.1 targets < 1000 ppm in occupied space. Use a non-dispersive infrared (NDIR) sensor — it does not drift like electrochemical types. Specify ≤ ±50 ppm + 3 % accuracy and a 7-day battery for survey work.

2. Particulate Matter (PM2.5 / PM10)

WHO 2021 guideline: PM2.5 24-hour mean < 15 µg/m³. Two sensor classes:

• Optical scatter (laser) — fast, cheap, good for trend monitoring; ±10 % typical.
• Gravimetric reference — used to calibrate and for regulatory submission.

3. Volatile Organic Compounds (VOCs)

A photo-ionisation detector (PID) covers most office and lab work; metal-oxide (MOX) sensors are cheaper but cross-sensitive. Expect ppb-level resolution; use the reading as a relative trend, not a public-health absolute.

4. Formaldehyde

Newly built or renovated spaces leak formaldehyde from MDF, carpets and adhesives. WHO 30-min limit: 100 µg/m³. Electrochemical sensors are the workhorse but drift fast — calibrate every 3–6 months.

5. Temperature and Relative Humidity

The forgotten driver of mould, dust mites and respiratory comfort. Target 20–24 °C, 40–60 % RH. Use a thin-film polymer humidity sensor with ±2 % RH accuracy. Pair with a wet-bulb / dew-point calculation for HVAC commissioning.

6. Combine Them in One Logger

Modern multi-parameter IAQ instruments capture all five plus CO and pressure differential, time-stamped to a memory card, with USB or Wi-Fi upload. EK air-quality loggers ship with a CSV export and built-in graph engine — handy for landlord reports.

Sampling Methodology Matters

1. Sample at breathing height (1.1 m seated, 1.5 m standing).
2. Avoid placement near doors, windows, supply diffusers.
3. Log for at least 7 days to capture occupancy variation.
4. Cross-reference HVAC schedule, occupancy and outdoor weather.
5. Use the same instruments on the next survey for trend comparison.