Mold risk score vs an indoor air quality monitor
Mold risk assessment vs indoor air quality monitor: no consumer monitor detects mold. It reads particulate, VOCs and humidity continuously; the assessment estimates the building's conditions.
A modelled mold risk assessment vs An indoor air quality monitor
| Axis | A modelled mold risk assessment | An indoor air quality monitor |
|---|---|---|
| What it actually measures | Conditions from records: climate, terrain, construction era and materials, documented water history. | Particulate counts, total VOCs, carbon dioxide and relative humidity in the air immediately around the device, continuously. |
| What it cannot see | Anything inside the building. | Mold. No consumer monitor identifies fungal spores or distinguishes them from any other particulate, and none claims to under examination. |
| Cost range (USD) | $0, $29, or $79 with disclosure analysis. | $100–$300 for a consumer unit, sometimes with a subscription for history and alerts. |
| Time to result | Seconds, before you have access. | Immediate readings, and genuinely useful over weeks — a season of humidity history is worth more than any single reading. |
| When it is required or accepted | Never required. | Never required. |
| Who accepts it (lender / insurer / court / buyer) | By nobody as evidence. | By nobody as evidence of mold. Its humidity history can be a useful supporting record in a landlord dispute. |
Buy the monitor for humidity, not for mold
An air quality monitor is a genuinely good purchase and a genuinely bad mold detector. The humidity channel is the valuable one: a device logging how often a room spends time above 60% relative humidity, and for how long, is measuring the persistence that actually decides whether anything grows. The particulate and VOC channels will move when you cook, hoover or light a candle, and interpreting those movements as mold is how people end up alarmed about dinner.
Why particulate counts do not mean mold
Consumer particulate sensors count particles by size — usually PM2.5 and PM10 — using light scattering. They do not identify what the particles are. Cooking, candles, hoovering, a fire, outdoor air on a still day and traffic all move those numbers, frequently by more than a mold problem would.
Fungal spores are within the size range those sensors detect, so a spore does register. So does everything else at that size, and the sensor cannot tell you which.
Total VOC readings have the same problem in a different form. Microbial volatile compounds are VOCs, and so are cleaning products, new furniture, paint and cooking. A tVOC spike is not a mold signal.
What the humidity channel is worth
More than the rest of the device, for this purpose. A spot reading tells you about a moment; a logged season tells you how often the room is above 60% and for how long, which is the persistence that governs growth.
Place them where the problem would be, not where it is convenient. A basement and an upstairs room frequently differ by more than either occupant expects, and the difference between them is the diagnostic.
Remember the reading describes air, not surfaces. A room at a comfortable 45% can still have a wall behind furniture on an uninsulated exterior wall sitting well above 80% locally, and that is where growth happens. An infrared thermometer against the cold patch, compared with the room's dew point, is the two-minute check that closes that gap.
Using both
Score the property to establish whether it has structural reasons to be damp — era, cladding, terrain, documented history. That is the part a sensor can never know.
Put a logging monitor in the room the drivers point at, and leave it for a season.
If the humidity history is persistently high and the score explains why, you have both a cause and a confirmation, which is a much stronger position than either alone.
The basis for these figures
General US ranges for planning, not quotes. Consumer monitor pricing varies widely by sensor set and by whether a subscription is bundled.
Questions people ask
- Is there a mold sensor?
- Not as a consumer device. Products marketed that way are measuring particulate or VOCs and inferring. Identifying mold requires a laboratory looking at a physical sample.
- Mold IQ score vs air quality index — what is the difference?
- An air quality index describes air at a moment. A risk score describes a building's propensity over its life. The first changes when you cook; the second does not.
- My monitor shows a particulate spike. Should I worry?
- Check what you were doing. Cooking and hoovering are the usual causes. A sustained humidity problem is the reading that matters here, not a particulate spike.
- Can a monitor prove a rental is damp?
- Its humidity log is genuinely useful supporting evidence, especially over months. It is not proof of mold, and it works best alongside written reports to the landlord.