Start with your nose and your history. A persistent musty smell, allergy symptoms that ease when you leave the house, and any past leak or flood that was never professionally dried are stronger evidence than most test kits. The hardware-store petri dish kits are near useless, they grow mold from the spores present in all normal air and prove nothing about your walls.
Meaningful testing is professional: air sampling that compares indoor spore counts against outdoor baselines, surface sampling of suspect growth, and, just as important, moisture meters and thermal imaging to find where water is sitting, because moisture is where mold will be. Nonstop Restoration does free mold inspections in Calgary, Airdrie, Chestermere, Strathmore, Okotoks, and Canmore. If we find something, you get a scoped remediation plan. If we do not, you get to stop worrying. Either way you know: (403) 620-8489.