Model multi-stage filtration systems with pre-filters and final filters. Calculate overall system efficiency, pressure drop stack, and particle removal by size fraction from MERV 8 through HEPA.
Size standalone air purifiers from room volume and target ACH. Calculate CADR needed for smoke, dust, and pollen. Covers portable units and whole-home systems.
Convert raw pollutant concentrations (PM2.5, PM10, O3, NO2, SO2, CO) to Canada's AQHI and the US AQI. Compare readings against AQHI risk categories and WHO guideline levels.
Calculate CO buildup from combustion appliances in enclosed spaces. Estimate time to hazardous concentrations and the ventilation needed to stay below Health Canada's 10 ppm 24-hour guideline.
Calculate steady-state indoor CO2 from occupancy, metabolic rate, and outdoor air flow. Compare with the 700 ppm above outdoor rule of thumb and Health Canada's 1,000 ppm limit, and size OA for any target.
Size the combustion air supply opening for gas furnaces, boilers, and water heaters using CSA B149.1 rules, and screen for backdrafting risk from exhaust fans and dryers.
Calculate the outdoor airflow needed to dilute CO2, formaldehyde, solvents, or any contaminant to a target concentration, with a mixing factor and purge time after the source stops.
Estimate indoor formaldehyde concentration from off-gassing materials and ventilation rate. Compare against Health Canada's 50 µg/m³ long-term guideline and size OA to achieve compliance.
Check HEPA face velocity against the rated value, estimate pressure drop and capture efficiency, and project filter service life from airflow and dust loading.
Check indoor humidity against Health Canada's 30 to 35% winter and under 50% summer ranges. Get dew point, mold, dust mite, and condensation risk from temperature and relative humidity.
Score overall indoor air quality from CO2, PM2.5, TVOC, formaldehyde, humidity, temperature, and ventilation. Get a composite index and find the weakest parameter.
Size bipolar ionization systems from ion output and airflow, and estimate room ozone from a test chamber reading against Health Canada's 20 ppb 8-hour guideline.
Compare filter efficiency across MERV 8 through MERV 16 and HEPA by particle size, and estimate pressure drop against your static pressure budget and face velocity.
Assess mold growth risk from surface temperature and ambient RH. Calculate surface relative humidity from indoor conditions and assembly RSI. Flags risk above 80% surface RH.
Estimate indoor PM2.5 concentration from outdoor levels, infiltration rate, filtration, and a portable purifier. Compare against the WHO 24-hour and annual guidelines.
Model indoor pollutant buildup and decay from any source rate, room volume, and ventilation. Works for CO, CO2, VOCs, PM2.5, and custom contaminants with time-to-threshold output.
Estimate suction points, fan pressure, and airflow for radon mitigation from soil type and slab area. Compares your level with Health Canada's 200 Bq/m³ guideline.
Find the UV-C dose, exposure time, and in-duct zone length needed for a target inactivation of airborne viruses and bacteria, using published UV rate constants.
Look up ASHRAE 62.1 zone air distribution effectiveness (Ez) for your supply and return layout, and get the corrected outdoor airflow for mixed, displacement, and floor supply systems.
Estimate TVOC from new construction materials, furniture, and finishes, the ventilation needed for a target, and how long decaying sources take to clear.
Indoor Air Quality Tools for Canadian Homes and Buildings
Indoor air quality has moved from a niche building science topic to a mainstream concern for Canadian homeowners and HVAC professionals alike, driven by wildfire smoke seasons, tighter building envelopes, and growing awareness of how much time we spend indoors. These 20 calculators cover the full range of IAQ assessment: pollutant-specific tools for CO2, PM2.5, VOCs, formaldehyde, carbon monoxide, and radon; filtration sizing for MERV, HEPA, and multi-stage systems; ventilation calculators for dilution air, combustion air, and ventilation effectiveness; and humidity-driven tools for mold risk and comfort assessment.
Where to Start
- For an overall snapshot, start with the IAQ calculator, which combines CO2, PM2.5, VOC, humidity, and ventilation into one composite score.
- During wildfire smoke season, use the PM2.5 calculator and air purifier sizing calculator together to plan filtration response.
- For new construction or renovation off-gassing, check the VOC calculator and formaldehyde calculator.
- If you've tested for radon above 200 Bq/m³, the radon mitigation calculator sizes the sub-slab depressurization system.
- For HVAC filter upgrades, compare options with the MERV rating calculator before committing to a MERV 13 retrofit.
Frequently Asked Questions
A space with CO2 below 1,000 ppm, PM2.5 within the WHO 24-hour guideline of 15 µg/m³, relative humidity between 30 and 50 percent, and no significant VOC sources scores in the Excellent or Good range on the IAQ calculator's composite index. Use the IAQ calculator to get a composite score from your own sensor readings.
Health Canada's long-term limit for CO2 in homes is 1,000 ppm as a 24-hour average. A common rule of thumb, which Health Canada attributes to ASHRAE, keeps CO2 within 700 ppm of outdoor levels, roughly 1,125 ppm with outdoor CO2 near 425 ppm. ASHRAE 62.1 itself sets ventilation rates rather than a CO2 limit, so a reading above these numbers means the space is under-ventilated for its occupancy. Use the CO2 level calculator to check your space against occupancy and ventilation rate.
Health Canada's guideline is 200 becquerels per cubic metre as the average annual radon concentration in normal occupancy areas. Its current guidance recommends taking action within one year when a long-term test shows a level above 200 Bq/m³, and sooner when the level is higher. Tests should run 91 days or more. Use the radon mitigation calculator to estimate the suction points and fan for a sub-slab depressurization system for your soil type and slab area.
A furnace filter upgrade (MERV 13 or better, if the system can handle the pressure drop) cleans all air circulating through your HVAC system whenever the fan runs, providing whole-home protection. A portable HEPA purifier cleans air in one room continuously, independent of furnace cycling, which is useful for bedrooms during sleep or homes without mechanical ventilation. During wildfire smoke events, combining both provides the strongest protection. Compare options with the MERV rating calculator and air purifier sizing calculator.
Yes. All AskHVAC.ca tools are fully responsive and work on any smartphone or tablet without an app install. Results can be exported to PDF or CSV directly from your phone. Use them freely at the job site, in the truck, or in the office.