Indoor Air Quality

Indoor Air Quality Instruments – CO2 Meters, Humidity Meters & IAQ Monitors for HVAC Technicians

Indoor air quality (IAQ) is increasingly part of the HVAC technician's scope of work. Whether you're commissioning a ventilation system, troubleshooting a comfort complaint, or conducting a building assessment, the right IAQ instrument gives you the data to diagnose the problem and back up your recommendations with numbers.

This collection covers CO2 meters, thermohygrometers, multi-parameter IAQ monitors, and related instruments from Testo, Fieldpiece, and Uni-T.

Key IAQ Parameters and What They Tell You

What's in This Collection

• CO2 meters — NDIR sensor instruments for measuring carbon dioxide concentration as a proxy for ventilation adequacy. Essential for HVAC commissioning, ventilation compliance, and building assessments.
• Thermohygrometers — combined temperature and relative humidity meters with dew point calculation. Used for mould risk assessment, comfort checks, and commissioning documentation.
• Multi-parameter IAQ monitors — instruments that measure CO2, temperature, humidity, and sometimes VOCs or particulates in a single unit.
• Data loggers — for long-term monitoring of temperature and humidity trends in buildings, cold rooms, and server rooms.

Related Categories

• Test & Measurement Tools — browse the full range of HVAC diagnostic instruments
• Testo HVAC Instruments — Testo CO2 meters, thermohygrometers, and Smart Probes
• Bluetooth Smart Tools — wireless IAQ instruments with app connectivity and data logging
• Thermal Imaging Cameras — identify condensation risk and moisture ingress visually

Frequently Asked Questions

What CO2 level indicates poor ventilation?

Outdoor CO2 is approximately 400–420 ppm. In occupied spaces, CO2 above 1000 ppm typically indicates inadequate fresh air supply. Above 1500 ppm, occupants often report stuffiness, headaches, and reduced concentration. ASHRAE and Australian standards use CO2 as a proxy for ventilation rate in occupied buildings.

Do I need a CO2 meter or a full IAQ monitor?

For ventilation commissioning and compliance checks, a dedicated CO2 meter is usually sufficient. For broader building assessments — particularly where mould risk, humidity, or VOC complaints are involved — a multi-parameter IAQ monitor gives you more data in a single instrument.

Can I use a thermohygrometer to assess mould risk?

Yes. By measuring surface temperature (with an IR thermometer) and ambient dew point (from a thermohygrometer), you can identify surfaces at risk of condensation and mould growth. Testo instruments with dew point calculation make this workflow straightforward.