Air Quality Canada
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24 companies listed · 7 in Markham · 9 open 24/7 · 21 open weekends · 22 rated 4.5+
Data verified October 18, 2026
Listed for homeowners in and around Markham, ON, these 24 companies test for mould and indoor air problems. Listings show what each one states about sampling, lab work and the environmental tests it offers, plus ratings and quotes from public reviews.

7 of the 24 companies we list are based in Markham; the other 17 serve Markham from towns including Scarborough (15 km), Newmarket (25 km) and Vaughan (20 km). 23 of the companies on this page have a rating, from 3.8 to 5.0 across 1,637 reviews; 12 have 50 or more reviews and 22 are rated 4.5 or higher. When customers rate these companies on specific qualities, they most often praise professionalism (91%), quality (82%) and responsiveness (80%). The topics that come up most in reviews of the companies on this page are "price", "efficient" and "estimates". 9 are open around the clock; 21 are open on Saturdays and 18 on Sundays. The services the companies on this page list most often on their websites are mold remediation (3), asbestos abatement (2), asbestos removal (2) and water damage restoration (2). 1 shows a licence on its website and 3 list staff certifications (IICRC). 8 have ten or more years of experience, the longest 30 years. 10 offer emergency call-outs; 2 offer financing or payment plans; 9 give free estimates and 3 are family- or locally-owned. We count these figures across the companies on this page; distances are straight-line, and hours and prices change, so confirm the details with the company before you book.
Sites are listed for 23 of the 24 companies here. Check whether the company sells removal as well as testing, which lab it sends samples to, and whether it shows a redacted sample report. A firm that explains its sampling method in public is easier to hold to it later.