Understand What Your Indoor Air Readings Mean
Purify uses specialized indoor-air monitoring equipment to assess particulate matter (PM), volatile organic compounds (VOCs) and carbon dioxide (CO₂). Readings are interpreted in context with the space, ventilation, occupancy and the concern being investigated.
What’s the Air Like Where You Are?
Check current outdoor air quality for a city or region anywhere in the world. Enter your location below, or allow your browser to use your location.
Location access is optional. Purify only uses it to request the nearby air-quality reading.
What Do PM, VOC and CO₂ Readings Mean?
The chart below is an educational reference based primarily on Health Canada, World Health Organization and German Environment Agency guidance. It is not a diagnosis and a brief monitor reading is not the same as a guideline averaging period.
| Measurement | Lower / preferred reference | Elevated / investigate | Higher concern | How to interpret it |
|---|---|---|---|---|
| PM2.5 µg/m³ |
≤ 15WHO 24-hour AQG | 15.1–50Above AQG; WHO interim-target range | > 50Above WHO Interim Target 2; investigate sources and exposure | Fine particles from smoke, cooking, combustion, dust and outdoor infiltration can raise PM2.5. A spot reading should be considered alongside duration and repeated measurements. |
| PM10 µg/m³ |
≤ 45WHO 24-hour AQG | 45.1–100Above AQG; WHO interim-target range | > 100Above WHO Interim Target 2; investigate sources and exposure | PM10 includes larger inhalable particles such as dust and other airborne debris. Indoor activities can create short spikes that need context. |
| CO₂ ppm |
< 1,000Health Canada 24-hour exposure limit; German UBA: hygienically safe | 1,000–2,000German UBA: hygienically noticeable | > 2,000German UBA: hygienically unacceptable | CO₂ is commonly used as an indicator of ventilation and occupancy. Elevated readings can point to a need to review outdoor-air exchange. |
| TVOC mg/m³ |
≤ 0.3German UBA hygienic reference: safe | > 0.3–3Increasing VOC load; source review may be useful | > 3German UBA: elevated concern; >10 unacceptable | TVOC is a broad indicator, not a health diagnosis. Different VOC mixtures have different health significance; specific compounds may require targeted or laboratory testing. |
| Formaldehyde (HCHO) µg/m³ |
≤ 50Health Canada 8-hour residential guideline | 50.1–123Above 8-hour guideline | > 123Above Health Canada 1-hour guideline | Shown for education because formaldehyde is a common indoor VOC. It is not measured in every Purify assessment; the test method depends on the concern and equipment used. |
Important: WHO PM values shown are 24-hour guideline values, Health Canada CO₂ is a 24-hour exposure limit, and Health Canada formaldehyde values use 8-hour and 1-hour averaging periods. A handheld or short-duration reading should not be treated as proof that a health guideline has been met or exceeded.
Specialized Indoor Air Quality Monitoring
We look at airborne particle levels and patterns that may be associated with smoke, dust, cooking, combustion, outdoor infiltration or other sources.
VOC readings can help identify when the total chemical load in the air is elevated. Paints, cleaners, fragrances, furnishings, building materials and combustion can contribute.
CO₂ is useful for understanding occupancy and ventilation conditions. Persistent elevation can indicate that outdoor-air exchange should be reviewed.
Comparing readings in different areas can help reveal patterns that a single measurement may miss. The assessment may include up to three areas, depending on the service selected.
A Reading Is a Clue — Not a Diagnosis
Indoor air changes throughout the day. Cooking, cleaning, open windows, HVAC operation, occupancy, weather, wildfire smoke and nearby traffic can all affect measurements.
For that reason, Purify looks at the reading together with the property, the concern, the location of the monitor and the conditions at the time of testing. Where a concern requires identification of a specific chemical, mould, allergen or other contaminant, targeted sampling or accredited laboratory analysis may be recommended.
What customers receive
- Indoor air quality measurements for the selected areas
- Plain-language explanation of notable readings and patterns
- Practical next-step recommendations within the scope of the assessment
- A written report when included with the selected service
- Recommendation for qualified or laboratory testing when appropriate
Indoor Air Testing FAQ
What is a good PM2.5 reading indoors?
WHO's 2021 air-quality guideline for PM2.5 is 15 µg/m³ as a 24-hour average. A short indoor reading below that level can be reassuring, but it is not equivalent to a 24-hour measurement and should be interpreted in context.
What CO₂ level suggests that ventilation should be reviewed?
Health Canada uses 1,000 ppm as a 24-hour residential exposure limit. The German Environment Agency classifies 1,000–2,000 ppm as hygienically noticeable and recommends increased ventilation, while levels above 2,000 ppm are considered hygienically unacceptable.
Does a TVOC number tell me which chemical is present?
No. TVOC is a combined indicator of many volatile organic compounds. It can show that VOC loading is elevated, but it does not identify the individual compounds or their specific health risk. Targeted sampling may be required.
Can an indoor air monitor diagnose mould or a medical condition?
No. Particle, VOC and CO₂ monitoring does not diagnose illness and cannot by itself identify mould species or prove the source of a health symptom. Laboratory or qualified specialist testing may be required for specific concerns.
Where These Reference Values Come From
The educational chart is built from recognized public-health and indoor-air guidance rather than a manufacturer chart.
Start With an Air Consultation
Tell us what you are experiencing, where it is happening and what type of property is involved. We can help determine the appropriate starting point.
Request Air Consultation