Interestingly enough, the best solutions come from both parts working together. In this example, the conservative view is indeed correct, it is very, very dangerous if you could disable a true alert. However, the progressive view still has a darn realistic point.

But, once you combine both, you reach a really interesting third way: Don't do binary detection, do trinary detection if possible. "No smoke", "Some smoke" and "Ok this is completely fubar"-levels of smoke. "Some smoke" can be waved, Fubar-Levels of smoke cannot be waved and the user is informed of this.