Why it matters
An Air Quality Index converts several separate pollutant readings into one number on a coloured scale, which makes it readable by anyone. That convenience comes at a cost: an index hides which parameter actually failed, and a “good” composite can conceal one pollutant sitting at its limit.
The audible alarm matters more than the index. Most indoor air problems develop slowly, and nobody watches a display continuously, so the alarm is what converts a monitor from a gadget into a control.
World standards
There is no single international AQI. The scale most consumer monitors use is derived from the US EPA index, which is built for outdoor ambient air. WHO publishes health-based guideline concentrations for individual pollutants rather than a composite index, which is why a monitor can read “good” while exceeding a WHO guideline.
Reference: WHO Global Air Quality Guidelines, 2021; US EPA Technical Assistance Document for the Reporting of Daily Air Quality.
UAE standards
Dubai Municipality assesses each parameter against the limits in its Tables 1, 2 and 3 individually. Formal compliance requires:
- 8-hour sampling, or an accepted surrogate of half-hour measurements across four time slots
- Testing by a company or laboratory accredited by the Emirates International Accreditation Centre
- Calibrated instruments with initial and periodic calibration certificates retained for inspection
- Probes 150 to 200 cm from walls and 100 to 200 cm above floor, away from diffusers, direct sunlight and the operator’s breath
- A minimum number of sampling points scaled to floor area, starting at one per 500 m²
DM does mandate audible alarms in one specific case: enclosed car parks must sound an alarm when carbon monoxide reaches 75 ppm, with sensors recalibrated every six months.
Reference: DM-HSD-GU119-IAQ Version 3 (2024), sections 9-5, 9-7 and 9-8.
Impact on health
The practical risk is false reassurance. A monitor showing a green index is not evidence of compliance and will not satisfy an inspector. The reverse also happens: an uncalibrated consumer sensor reporting alarming numbers causes unnecessary worry and expensive investigation of a fault that does not exist.
How to use a monitor properly
- Use a continuous monitor for early warning and trend detection, and accredited testing for compliance. They answer different questions and neither replaces the other
- Set individual alarm thresholds rather than relying on the composite index: CO₂ at 800 ppm, HCHO at 0.08 ppm, relative humidity at 60%
- Position the monitor per the DM probe rules. A unit sitting on a desk under a diffuser reports the diffuser, not the room
- Recalibrate or replace sensors on the manufacturer’s schedule. Electrochemical and metal-oxide sensors drift, and a three-year-old uncalibrated monitor is a decoration
- When an alarm triggers repeatedly in one zone, trace it rather than silencing it. DM’s own approach is source identification first, sampling second
Need this equipment serviced?
Inspection first, fixed written price before any work begins, and a photo report on completion.