Smoke testing involves pumping smoke through your sewer pipes under light pressure. In this case, where there’s smoke, there’s a leak allowing sewer gas to escape.
This method requires relatively little setup and can test the whole system’s efficiency under normal working conditions. The smoke is non-toxic and non-hazardous, leaves no stains, and has no negative effect on plants or animals.
The smoke should not enter your premises, but if it does it will have a distinct odor that should only last a few minutes with proper ventilation.