PM Readings Stay at Zero

If your PM1, PM2.5 or PM10 readings remain at or close to 0 µg/m³, this is usually not a sign that Airmonitor Plus is faulty.

Particulate matter sensors only detect airborne particles. If the air is very clean, it's perfectly normal for the readings to remain at or near zero.

What Does PM Measure?

Airmonitor Plus measures three sizes of airborne particles:

• PM1 – Ultra-fine particles.
• PM2.5 – Fine particles such as smoke and cooking fumes.
• PM10 – Larger particles such as dust and pollen.

These particles are only detected when they are suspended in the air.

Why Are My Readings So Low?

Many homes have very low particulate levels, particularly if:

• Windows are closed.
• An air purifier is being used.
• The room has recently been cleaned.
• There are no active sources of smoke or dust.

In these situations, PM readings close to zero are completely normal and indicate clean indoor air.

How Can I Check the PM Sensor Is Working?

The easiest way to confirm the particle sensor is responding is to expose Airmonitor Plus to a temporary source of airborne particles.

Examples include:

• Cooking, especially frying or grilling.
• Blowing out a candle.
• Lighting a match.
• Vacuuming.

The PM readings should begin to rise within a short period before gradually returning to normal as the air clears.

Important: Do not expose Airmonitor Plus to excessive smoke or large amounts of dust, as unnecessarily high concentrations may reduce sensor performance over time.

Why Do PM Readings Change So Quickly?

Unlike gases such as CO₂, airborne particles can appear and disappear very rapidly.

For example, cooking or blowing out a candle may cause PM2.5 levels to rise within seconds before gradually falling as the particles settle or are removed through ventilation.

Rapid changes in PM readings are completely normal.

Frequently Asked Questions

Is a zero PM reading normal?

Yes. If the air is very clean, PM1, PM2.5 and PM10 readings may remain at or close to zero.

Does a zero reading mean the particle sensor isn't working?

No. The sensor only detects airborne particles. If very few particles are present, the readings will remain low.

Which everyday activities increase PM readings?

Common sources include:

1. Cooking.
2. Candles.
3. Fireplaces.
4. Tobacco smoke.
5. Incense.
6. Vacuuming.
7. Dusting.
8. Wildfire smoke entering from outdoors.

Why does PM2.5 increase but CO₂ doesn't?

PM and CO₂ measure completely different things. PM measures airborne particles, while CO₂ measures carbon dioxide gas. One can increase without affecting the other.

When should I contact Breathe Tech Support?

If the PM readings never change after several days of normal use, including during activities such as cooking or lighting a candle, please contact Breathe Tech Support. We'll be happy to help you check that your monitor is operating correctly.