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15 companies listed · 7 in Markham · 6 open 24/7 · 11 open weekends · 12 rated 4.5+
Data verified October 18, 2026
Listed for homeowners in and around Markham, ON, these 15 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 15 companies we list are based in Markham; the other 8 serve Markham from towns including Scarborough (15 km), Richmond Hill (14 km) and Thornhill (15 km). 14 of the companies on this page have a rating, from 3.8 to 5.0 across 1,295 reviews; 8 have 50 or more reviews and 12 are rated 4.5 or higher. When customers rate these companies on specific qualities, they most often praise professionalism (96%), quality (85%) and responsiveness (85%). The topics that come up most in reviews of the companies on this page are "price", "efficient" and "estimates". 6 are open around the clock; 10 are open on Saturdays and 10 on Sundays. 3 list staff certifications (IICRC and InterNACHI). 3 have ten or more years of experience, the longest 30 years. 7 offer emergency call-outs; 6 give free estimates and 2 are family- or locally-owned. We have a website on file for 14 of the companies on this page; 12 publish a contact page; 13 list a public email and 2 take bookings online. 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.
Not when the first visit ends with a large removal quote attached. You have 15 companies on this page, so getting a second diagnosis is straightforward. Ask each one what it thinks the water source is. Two independent answers that match is the strongest signal you will get.
