{"id":4760,"date":"2026-08-06T09:05:39","date_gmt":"2026-08-06T13:05:39","guid":{"rendered":"https:\/\/ventiloexpair.com\/guides-news\/analyse-de-lair-dans-une-maison\/"},"modified":"2026-08-06T09:14:32","modified_gmt":"2026-08-06T13:14:32","slug":"when-to-do-it-whats-measured-and-how-to-interpret-the-results","status":"publish","type":"post","link":"https:\/\/ventiloexpair.com\/en\/guides-news\/when-to-do-it-whats-measured-and-how-to-interpret-the-results\/","title":{"rendered":"Indoor Air Quality Testing: When to Do It, What&#8217;s Measured, and How to Interpret the Results"},"content":{"rendered":"<p>An indoor air quality test measures what your senses can&#8217;t detect: excessive humidity, mold spores, carbon monoxide, radon, and volatile organic compounds. It&#8217;s performed when symptoms persist, after water damage, or before buying a home.<\/p>\n<h2><b>Key points to remember<\/b><\/h2>\n<ul>\n<li aria-level=\"1\">According to the INSPQ, the optimal relative humidity in a Quebec home is between <b>30 and 50 percent<\/b>; above that level, mold and dust mites thrive.<\/li>\n<li aria-level=\"1\">The long-term residential exposure limit for carbon dioxide set by Health Canada is <b>1,000 ppm<\/b> (24-hour average).<\/li>\n<li aria-level=\"1\">The Canadian guideline for radon in indoor air is <b>200 Bq\/m\u00b3<\/b>, and screening requires a measurement taken over <b>a minimum of 3 months<\/b> during the heating season.<\/li>\n<li aria-level=\"1\">A bacteriological and fungal analysis of the air is performed using <b>volumetric sampling<\/b>, with a reference outdoor sample collected on the same day.<\/li>\n<li aria-level=\"1\">A test alone does not solve the problem; it helps identify the source of moisture and the <b>ventilation<\/b> issues that need to be addressed.<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-4752\" title=\"Air Quality Analysis in a Home\" src=\"https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/analyse-de-lair-dans-une-maison-1024x683.png\" alt=\"Air Quality Analysis in a Home\" width=\"600\" height=\"400\" srcset=\"https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/analyse-de-lair-dans-une-maison-1024x683.png 1024w, https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/analyse-de-lair-dans-une-maison-300x200.png 300w, https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/analyse-de-lair-dans-une-maison-768x512.png 768w, https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/analyse-de-lair-dans-une-maison.png 1536w\" sizes=\"(max-width: 600px) 100vw, 600px\" \/><\/p>\n<p>Measurements are taken in rooms that are normally occupied, including the basement.<\/p>\n<h2><b>When an air analysis Becomes Truly Necessary<\/b><\/h2>\n<p>Most homes do not need an annual test. There are four situations that warrant one. First, <b>symptoms that follow the home<\/b>: congestion, coughing, eye irritation, or headaches that subside when the occupants are away for a few days. The Quebec government directly links these symptoms to prolonged exposure to <a href=\"https:\/\/www.quebec.ca\/sante\/problemes-de-sante\/a-z\/problemes-de-sante-causes-par-les-moisissures\" target=\"_blank\" rel=\"noopener\">mold in residential settings<\/a>.<\/p>\n<p>Next, <b>water damage<\/b>: seepage through the foundation, sewer backup, a hole in the roof, or a frozen pipe. Mold can colonize a damp drywall panel within <b>24 to 48 hours<\/b>. Third scenario: a <b>persistent earthy or musty odor<\/b> with no visible signs <b>of<\/b> moisture, typically in a crawlspace, an attic, or behind wall paneling. Fourth scenario: a <b>real estate transaction<\/b> or rental dispute, where a dated laboratory report serves as evidence that a visual inspection alone cannot provide.<\/p>\n<p>Conversely, if a 30-cm black stain is visible behind a washing machine, an analysis is often unnecessary: the source has been identified, so it\u2019s time <a href=\"https:\/\/ventiloexpair.com\/service\/prevention-et-traitement-de-la-moisissure\/\">to move on to correcting the issue and treating the mold<\/a>.<\/p>\n<h2><b>What We Actually Measure in a House<\/b><\/h2>\n<p>&#8220;Air analysis&#8221; encompasses several distinct measurements, each with different methods and durations. Confusing them is the leading cause of unusable results.<\/p>\n<table>\n<thead>\n<tr>\n<th>Parameter<\/th>\n<th>Method<\/th>\n<th>Sampling duration<\/th>\n<th>Reference point<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Relative Humidity<\/td>\n<td>Hygrometer \/ Logger<\/td>\n<td>7 to 14 days<\/td>\n<td>30 to 50% (INSPQ)<\/td>\n<\/tr>\n<tr>\n<td>Carbon dioxide (CO\u2082)<\/td>\n<td>Infrared sensor<\/td>\n<td>24 to 72 hours<\/td>\n<td>1,000 ppm over 24 hours (Health Canada)<\/td>\n<\/tr>\n<tr>\n<td>Mold Spores<\/td>\n<td>Volumetric sampling on cassette<\/td>\n<td>5 to 15 minutes per room<\/td>\n<td>Comparison with outdoor levels<\/td>\n<\/tr>\n<tr>\n<td>Aerobic bacteria<\/td>\n<td>Agar plating, laboratory culture<\/td>\n<td>Analysis takes 3 to 7 days<\/td>\n<td>Comparison with external samples<\/td>\n<\/tr>\n<tr>\n<td>Radon<\/td>\n<td>Passive alpha detector<\/td>\n<td>At least 3 months<\/td>\n<td>200 Bq\/m\u00b3 (Health Canada)<\/td>\n<\/tr>\n<tr>\n<td>Carbon monoxide (CO)<\/td>\n<td>Electrochemical detector<\/td>\n<td>Continuous measurement<\/td>\n<td>Any sustained reading requires venting<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>CO\u2082 deserves some clarification: it is not toxic at residential concentrations, but it is the best <b>indirect indicator of air exchange rate<\/b>. Health Canada explains this in its <a href=\"https:\/\/www.canada.ca\/fr\/sante-canada\/services\/publications\/vie-saine\/lignes-directrices-qualite-air-interieur-residentiel-dioxyde-carbone.html\" target=\"_blank\" rel=\"noopener\">guidelines on residential indoor air quality<\/a>. A closed bedroom where levels rise to 1,800 ppm at night does not indicate the presence of a toxin; it indicates that fresh air is not entering the room.<\/p>\n<h2><b>How Is an Indoor Air Quality Test Conducted?<\/b><\/h2>\n<p>A typical inspection of a single-family home lasts <b>between 90 minutes and 3 hours<\/b> and always follows the same sequence. First, a visual and olfactory inspection is conducted, room by room, including the basement, crawl space, and attic. Next, we use a thermo-hygrometer and a moisture meter to test suspicious materials. Only then do we take air samples, because the results can only be interpreted in light of what we\u2019ve observed.<\/p>\n<p>Two rules determine the validity of a fungal sample. An <b>outdoor reference sample<\/b> must be collected on the same day, at the same time: without it, an indoor count is meaningless, since spores occur naturally everywhere. Additionally, <b>doors and windows must remain closed for 12 to 24 hours prior to<\/b> the visit, with mechanical ventilation operating normally.<\/p>\n<p>When the suspected source is located within the distribution system, air sampling is accompanied by a <a href=\"https:\/\/ventiloexpair.com\/service\/inspection-robotisee-et-visuelle\/\">robotic inspection of the ducts<\/a>: the camera reveals buildup, construction debris, or traces of water, which the laboratory will simply confirm.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-4754\" title=\"How to Read a Lab Report Without Getting Scared\" src=\"https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/lire-un-rapport-de-laboratoire-sans-se-faire-peur-1024x683.png\" alt=\"How to Read a Lab Report Without Getting Scared\" width=\"600\" height=\"400\" srcset=\"https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/lire-un-rapport-de-laboratoire-sans-se-faire-peur-1024x683.png 1024w, https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/lire-un-rapport-de-laboratoire-sans-se-faire-peur-300x200.png 300w, https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/lire-un-rapport-de-laboratoire-sans-se-faire-peur-768x512.png 768w, https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/lire-un-rapport-de-laboratoire-sans-se-faire-peur.png 1536w\" sizes=\"(max-width: 600px) 100vw, 600px\" \/><\/p>\n<p>Volumetric sampling requires a known flow rate and an external reference sample.<\/p>\n<h2><b>How to Read a Lab Report Without Getting Scared<\/b><\/h2>\n<p>A <a href=\"https:\/\/ventiloexpair.com\/service\/analyse-bacteriologique\/\">bacteriological and fungal analysis<\/a> report does not provide a score out of 100. It provides concentrations in CFU\/m\u00b3 or spores\/m\u00b3, a breakdown by genus, and the same count for outdoor samples. Interpretation is based on three questions.<\/p>\n<table>\n<thead>\n<tr>\n<th>What the report shows<\/th>\n<th>Common interpretation<\/th>\n<th>Action<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Interior is inferior to or comparable to the exterior; same types<\/td>\n<td>Normal condition<\/td>\n<td>Monitor humidity; no work required<\/td>\n<\/tr>\n<tr>\n<td>Upper Interior, same dominant genres<\/td>\n<td>Accumulation, often linked to insufficient ventilation<\/td>\n<td>Improve air circulation, clean<\/td>\n<\/tr>\n<tr>\n<td>Genus associated with persistent moisture (<i>Stachybotrys<\/i>, <i>Chaetomium<\/i>, hydrophilic <i>Aspergillus<\/i> )<\/td>\n<td>Active growth within the building<\/td>\n<td>Locate and cut off the water source; decontaminate<\/td>\n<\/tr>\n<tr>\n<td>Low counts but a distinct odor<\/td>\n<td>Colony hidden behind a material<\/td>\n<td>Targeted investigation, surface or material sampling<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>The INSPQ emphasizes this point in its framework for addressing <a href=\"https:\/\/www.inspq.qc.ca\/qualite-de-l-air-et-salubrite-intervenir-ensemble-dans-l-habitation-au-quebec\/qualite-de-l-air-et-salubrite\/parametres-de-confort\" target=\"_blank\" rel=\"noopener\">air quality and housing health<\/a>: there is no universal threshold value for mold in residential settings. The assessment is based on the difference between indoor and outdoor levels, the types of mold identified, and the actual condition of the building.<\/p>\n<h2><b>Radon: the only contaminant with a clearly defined threshold<\/b><\/h2>\n<p>Radon is a naturally occurring radioactive gas produced by the decay of uranium in the soil. It enters homes through cracks in the foundation slab, drains, and sump pits. It is <b>odorless and colorless<\/b>, and is the second leading cause of lung cancer in Canada. The <a href=\"https:\/\/www.canada.ca\/fr\/sante-canada\/services\/securite-et-risque-pour-sante\/radiation\/radon\/lignes-directrices-gouvernement-canada.html\" target=\"_blank\" rel=\"noopener\">federal guideline<\/a> is <b>200 Bq\/m\u00b3<\/b> for the average annual exposure in rooms that are normally occupied.<\/p>\n<p>Two practical implications. A <b>48-hour<\/b> test <b>is not sufficient<\/b>: concentrations vary by a factor of 2 to 5 depending on the season, atmospheric pressure, and ventilation operation, hence the requirement for a passive detector to be left in place <b>for at least 3 months<\/b>, ideally between November and April. And if the result exceeds 200 Bq\/m\u00b3, the solution involves actively depressurizing the floor, not simply adjusting the fan.<\/p>\n<h2><b>What analysis cannot replace: disaggregation<\/b><\/h2>\n<p>New homes in Quebec are airtight by design, which is great for heating bills but problematic for indoor air quality. Without mechanical ventilation, moisture produced by cooking, showering, and breathing remains inside. That\u2019s why analysis reports so often conclude with the same recommendation: run the <a href=\"https:\/\/ventiloexpair.com\/service\/nettoyage-dechangeurs-dair\/\">heat-recovery ventilator<\/a> continuously at a low setting and clean its filters.<\/p>\n<p><a href=\"https:\/\/www.epa.gov\/indoor-air-quality-iaq\/inside-story-guide-indoor-air-quality\" target=\"_blank\" rel=\"noopener\">The EPA<\/a> prioritizes ventilation and source control over any purification system: dilute and exhaust before filtering. Specifically, in a home where testing reveals a humidity level of 62% in January, the recommended sequence is as follows.<\/p>\n<ol>\n<li aria-level=\"1\">Check and correct sources of water ingress: drainage, caulking, and the slope of the ground.<\/li>\n<li aria-level=\"1\">Restore the measured airflow at the supply and exhaust grilles.<\/li>\n<li aria-level=\"1\">Clean the system and the heat exchanger if the inspection reveals fouling.<\/li>\n<li aria-level=\"1\">Repeat the moisture measurement over a two-week period to confirm the effect.<\/li>\n<\/ol>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-large wp-image-4757\" title=\"Seek professional help rather than relying on a first-aid kit\" src=\"https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/faire-appel-a-un-professionnel-plutot-qua-une-trousse-de-pharmacie-1024x377.png\" alt=\"Seek professional help rather than relying on a first-aid kit\" width=\"1024\" height=\"377\" srcset=\"https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/faire-appel-a-un-professionnel-plutot-qua-une-trousse-de-pharmacie-1024x377.png 1024w, https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/faire-appel-a-un-professionnel-plutot-qua-une-trousse-de-pharmacie-300x110.png 300w, https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/faire-appel-a-un-professionnel-plutot-qua-une-trousse-de-pharmacie-768x283.png 768w, https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/faire-appel-a-un-professionnel-plutot-qua-une-trousse-de-pharmacie-1536x565.png 1536w, https:\/\/ventiloexpair.com\/wp-content\/uploads\/2026\/08\/faire-appel-a-un-professionnel-plutot-qua-une-trousse-de-pharmacie.png 1600w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/p>\n<p>Key figures for homes in Quebec.<\/p>\n<h2><b>Seek professional help rather than relying on a first-aid kit<\/b><\/h2>\n<p>Retail test kits often rely on a Petri dish left open on a counter. The result is guaranteed to be positive: spores are present in any healthy home. Without a calibrated volumetric sample or an external reference, the data cannot be interpreted, and, more importantly, it provides no information about the location of the source.<\/p>\n<p>A professional service provides three things: a known sampling rate, an independent accredited laboratory, and a building inspection that links the measurement to a physical cause. For homes in the Granby and Haute-Yamaska areas,<a href=\"https:\/\/ventiloexpair.com\/entreprise-nettoyage-conduits-ventilation-granby\/\">the Ventilo Exp&#8217;Air team<\/a> combines analysis, duct inspection, and ventilation repairs into a single service call.<\/p>\n<h2><b>FAQ \u2014 Indoor Air Quality Testing<\/b><\/h2>\n<details open=\"\">\n<summary>How long does it take to get the results?<\/summary>\n<p>Instrument measurements (humidity, CO\u2082, CO) are taken on-site. Fungal and bacterial samples require laboratory culturing or microscopic counting, which generally takes 3 to 7 business days. Radon is the exception, requiring a 3-month sampling period.<\/p>\n<\/details>\n<details>\n<summary>Do I need to leave the house during the test?<\/summary>\n<p>No. In fact, the house should remain in its normal living condition. We simply ask that you keep the windows closed for 12 to 24 hours beforehand, avoid vacuuming right before the visit, and refrain from using scented products on the day of the test.<\/p>\n<\/details>\n<details>\n<summary>Can an air quality test detect hidden mold inside a wall?<\/summary>\n<p>Indirectly. A high indoor count of hydrophilic mold species indicates active growth somewhere, but locating the source requires an inspection using a moisture meter, a thermal imaging camera, or the targeted removal of building materials. This is why an air quality analysis is never offered on its own.<\/p>\n<\/details>\n<details>\n<summary>How often should the test be repeated?<\/summary>\n<p>There is no recommended testing frequency for a home where no symptoms are present. The analysis is typically repeated to verify that remediation work has been effective, after a new water damage incident, or when new occupants experience recurring symptoms.<\/p>\n<\/details>\n<details>\n<summary>Does cleaning air ducts improve indoor air quality?<\/summary>\n<p>Yes, when the duct system is genuinely contaminated\u2014such as after construction work, a fire, water damage, or in an older home that has never been maintained. However, it does not solve moisture problems or inadequate ventilation. Air duct cleaning is one part of the solution, not the entire solution.<\/p>\n<\/details>\n","protected":false},"excerpt":{"rendered":"<p>An indoor air quality test measures what your senses can&#8217;t detect: excessive humidity, mold spores, carbon monoxide, radon, and volatile organic compounds. It&#8217;s performed when symptoms persist, after water damage, or before buying a home. Key points to remember According to the INSPQ, the optimal relative humidity in a Quebec home is between 30 and [&hellip;]<\/p>\n","protected":false},"author":13,"featured_media":4753,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[2],"tags":[],"class_list":["post-4760","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-guides-news"],"acf":[],"_links":{"self":[{"href":"https:\/\/ventiloexpair.com\/en\/wp-json\/wp\/v2\/posts\/4760"}],"collection":[{"href":"https:\/\/ventiloexpair.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ventiloexpair.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ventiloexpair.com\/en\/wp-json\/wp\/v2\/users\/13"}],"replies":[{"embeddable":true,"href":"https:\/\/ventiloexpair.com\/en\/wp-json\/wp\/v2\/comments?post=4760"}],"version-history":[{"count":2,"href":"https:\/\/ventiloexpair.com\/en\/wp-json\/wp\/v2\/posts\/4760\/revisions"}],"predecessor-version":[{"id":4762,"href":"https:\/\/ventiloexpair.com\/en\/wp-json\/wp\/v2\/posts\/4760\/revisions\/4762"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ventiloexpair.com\/en\/wp-json\/wp\/v2\/media\/4753"}],"wp:attachment":[{"href":"https:\/\/ventiloexpair.com\/en\/wp-json\/wp\/v2\/media?parent=4760"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ventiloexpair.com\/en\/wp-json\/wp\/v2\/categories?post=4760"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ventiloexpair.com\/en\/wp-json\/wp\/v2\/tags?post=4760"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}