I think the difference comes down to prolonged exposure to lower levels (eg medium exposure) vs short-term exposure to high levels. The canary is for the latte

I think the difference comes down to prolonged exposure to lower levels (eg medium exposure) vs short-term exposure to high levels. The canary is for the latter scenario. If the EPA says it can kill "in minutes" [1], then I'd be inclined to believe them over "you'll feel it if you're exposed to it for hours". 1- https://www.epa.gov/indoor-air-quality-iaq/protect-your-family-and-yourself-carbon-monoxide-poisoning https://www.epa.gov/indoor-air-quality-iaq/protect-your-fami...