There are two types of smoke tests. In the one, we use a smoke generator capable of filling a space with particularly dense smoke, and then looking on the other side of (e.g.) a fire barrier or smoke seal to see if there is any leakage. The other type is with smoke pencils which are used to detect air moving into a joint in a system to get an idea of where a leak exists and its comparative size. We use these in Air Infiltration Tests, but also for diagnosis of air movement within buildings, for example in the investigation of humidity problems.