💨 CO2 Level
Result Breakdown
Full Calculation Table
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How to Use the Air Quality Test Calculator
Choose CO2, PM2.5, or VOC depending on which field meter reading you have on hand.
Enter the value from your meter. For CO2, note whether the space was occupied at the time of the reading, since occupancy affects interpretation.
Click Calculate Assessment to see the reading compared against Health Canada guidance and common field thresholds, along with a recommendation for next steps.
Understanding Indoor Air Quality Testing
Indoor air quality complaints often show up as vague symptoms like stuffiness, headaches, or general discomfort that are hard to pin down without a measurement. CO2, PM2.5, and VOC readings turn that vague complaint into actual data, pointing toward specific causes like inadequate ventilation, particulate infiltration, or off-gassing materials.
CO2 as a Ventilation Indicator
CO2 itself isn't harmful at typical indoor concentrations, but it serves as a useful proxy for ventilation adequacy, since exhaled breath is the dominant indoor CO2 source in most occupied spaces. Outdoor ambient CO2 sits around 420 ppm, and Health Canada's long-term exposure limit for CO2 in homes is 1000 ppm averaged over 24 hours, which this calculator uses as the top of its Good range. Because that limit is a 24-hour average, a single snapshot works as a screening check rather than a compliance result. As occupants breathe in a space without enough fresh air exchange, CO2 accumulates, and the degree of accumulation above outdoor levels roughly indicates how well ventilation is keeping pace with occupancy. A rising CO2 trend over the course of an occupied period, rather than a single snapshot reading, often tells the more useful story.
PM2.5 and Particulate Sources
PM2.5 refers to fine particulate matter small enough to penetrate deep into the respiratory system, with health effects that Health Canada and other agencies treat as significant even at relatively low concentrations. Indoor PM2.5 above outdoor ambient levels typically points to an indoor source, commonly cooking, combustion appliances without adequate venting, or inadequate filtration allowing outdoor particulate to accumulate indoors faster than it's removed. Comparing an indoor reading against a simultaneous outdoor reading helps distinguish an indoor source problem from a broader regional air quality event, which matters during wildfire smoke season in many parts of Canada. Health Canada's guidance for cleaner air spaces during smoke events takes the same approach, advising that indoor PM2.5 stay below the outdoor level.
VOCs and Off-Gassing
Volatile organic compounds come from a wide range of sources, including new building materials, furnishings, cleaning products, and some combustion processes. A basic VOC sensor gives a general index reading rather than identifying specific compounds, so higher VOC readings are best treated as a signal to investigate further rather than a definitive diagnosis of a specific chemical hazard. New construction or recently renovated spaces commonly show higher VOC readings that decline over the following weeks to months as materials off-gas and cure. Spaces with a low air change rate hold onto those compounds longer, and the air changes per hour calculator shows how a space's ventilation compares.
Connecting Readings to HVAC Action
Higher CO2 points toward increasing mechanical ventilation rate or verifying an existing ventilation system is actually functioning as designed, which can be checked with the ASHRAE 62.1 calculator for commercial spaces. Higher PM2.5 points toward filtration upgrades and confirming filter bypass isn't occurring, which the filter test calculator can help evaluate. Higher VOC often needs source identification and may resolve with time or improved general ventilation rather than an HVAC equipment change.
Documenting Indoor Air Quality Results
Recording readings alongside occupancy status, HVAC operating condition, and any known nearby sources like cooking or renovation activity gives useful context for interpreting results and tracking whether corrective action improved conditions. Include findings in a commissioning report or general test documentation for the project file.
Frequently Asked Questions
Outdoor CO2 is typically around 420 ppm. Health Canada's long-term exposure limit for homes is 1000 ppm averaged over 24 hours, and readings consistently above that generally indicate ventilation isn't keeping pace with occupancy. This calculator rates up to 1000 ppm as Good, 1000 to 1500 ppm as Higher, 1500 to 2000 ppm as High, and above 2000 ppm as Very High.
Health Canada advises keeping indoor PM2.5 as low as possible, since no threshold has been found that fully protects against health effects. As general reference points, this calculator rates up to 10 µg/m³ as Good, 10 to 25 µg/m³ as Higher, 25 to 35 µg/m³ as High, and above 35 µg/m³ as Very High. Indoor PM2.5 above outdoor ambient levels often points to an indoor source such as cooking, combustion appliances, or inadequate filtration.
Bringing in more outdoor air through proper mechanical ventilation directly reduces CO2 buildup from occupant respiration, while upgrading filtration and ensuring filters are properly sealed and regularly replaced reduces PM2.5 by capturing particulate matter circulating through the system. Check the filter test calculator to evaluate current filtration performance.
Test under normal operating conditions with the HVAC system running as it typically would during occupied hours, since this reflects the air quality occupants actually experience day to day. A comparison reading with ventilation temporarily increased can help demonstrate the effect of additional fresh air on CO2 levels specifically.
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