Indoor Air Quality Calculator

Enter your room dimensions, ventilation rate, and pollutant sources to estimate your Indoor Air Quality (IAQ). The calculator returns a pollutant concentration in µg/m³, an air quality index score, and a health risk rating — helping you understand whether your indoor environment meets safe exposure thresholds set by the EPA. Also try the find Estimated Sky Brightness (SQM) with Light Pollution Calculator.

m

Length of the indoor space in metres

m

Width of the indoor space in metres

m

Height of the room from floor to ceiling

ACH

Air Changes per Hour (ACH). Typical homes: 0.35–1 ACH; offices: 4–10 ACH.

µg/m³

Baseline ambient PM2.5 level outdoors. Check AirNow.gov for local values.

Select the primary source of indoor pollution in this space.

hrs/day

How many hours per day is this source active?

A HEPA purifier can significantly reduce particulate concentrations.

Results

Estimated Indoor PM2.5 Concentration

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Estimated AQI Score

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Health Risk Rating

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Source Emission Rate

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Purifier Reduction

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Frequently Asked Questions

What does an Indoor Air Quality Calculator measure?

It estimates the concentration of airborne pollutants — particularly PM2.5 fine particulate matter — inside a room based on its size, ventilation rate, outdoor air quality, and indoor emission sources. The result is expressed in µg/m³ and mapped to an Air Quality Index (AQI) score so you can compare against EPA health thresholds.

What is a safe indoor PM2.5 level according to the EPA?

The EPA's 24-hour PM2.5 standard is 35 µg/m³, while the annual standard is 12 µg/m³. For ongoing indoor exposure, levels below 12 µg/m³ are considered good. Concentrations between 35–55 µg/m³ are unhealthy for sensitive groups, and anything above 55 µg/m³ poses risks for the general population.

How does ventilation affect indoor air quality?

Ventilation dilutes indoor pollutants by replacing contaminated air with outdoor air. A higher Air Changes per Hour (ACH) rate flushes out pollutants faster, lowering steady-state concentrations. However, in areas with high outdoor pollution, increasing ventilation can also bring in more outdoor contaminants — so purifiers may be needed.

What is ACH (Air Changes per Hour)?

ACH measures how many times the total air volume in a room is replaced in one hour. A typical home has 0.35–1 ACH through natural infiltration. Mechanical ventilation systems in offices and commercial buildings typically deliver 4–10 ACH. Higher ACH values generally mean better dilution of indoor pollutants.

How effective is a HEPA air purifier at reducing pollutants?

A HEPA air purifier removes at least 99.97% of particles ≥0.3 µm in the air it processes. Its effectiveness in a room depends on its Clean Air Delivery Rate (CADR) relative to the room volume. A high-capacity unit (CADR ~350 m³/h) in a medium room can reduce PM2.5 concentrations by 50–70% when running continuously.

Which household activities produce the most indoor air pollution?

Gas cooking — especially frying or grilling — is one of the largest sources of indoor PM2.5, often spiking levels above 100 µg/m³ during cooking. Wood-burning fireplaces, cigarette smoking, burning candles or incense, and VOC-emitting cleaning sprays are also major contributors. Even laser printers release ultrafine particles during operation.

What is the difference between PM2.5 and AQI?

PM2.5 is a direct physical measurement of fine particulate matter concentration in micrograms per cubic metre (µg/m³). The AQI (Air Quality Index) is a standardised 0–500 scale that converts pollutant concentrations into a colour-coded category (Good, Moderate, Unhealthy, etc.) for easier public communication. This calculator converts PM2.5 to an estimated AQI using EPA breakpoints.

Can this calculator account for multiple pollutant sources at once?

Currently, the calculator models one primary source at a time combined with the outdoor background level. For spaces with multiple simultaneous sources — such as cooking while a fireplace is active — run separate estimates for each and consider the results additive. Selecting a higher-emission source and a longer activity duration provides a conservative worst-case estimate.