A Brief History of Smoke Tests
Smoke Defects
This photo shows smoke that has been introduced into a manhole by a high-capacity blower. A defect in the sewer pipe allows smoke to escape up through the ground The collage above depicts various areas of smoke emerging from possible defects during smoke testing

 

The process of testing a sanitary sewer system by introducing smoke into the network of pipes was first accomplished in McPherson, Kansas in 1961.  Smoke testing proved to have numerous advantages: the smoke was harmless, did not stain, and allowed sewer personnel to track down and localize defects in the system quickly and safely.  Smoke testing is endorsed by the Environmental Protection Agency. Hydrated zinc chloride is a commonly used smoking agent, producing a smoke that contains large quantities of atmospheric moisture--so a relatively small amount of smoke agent can produce a great deal of smoke.