The underlying principle at the back the employ of a bong is the maintain that the cooling result of the water helps to decrease the possibility of ablaze the mouth, airways, and lungs, thus many maintain that using a bong to smoke is safer. The water can trap some heavier particles and water-soluble molecules, preventing them as of incoming the smoker's airways. Thus the workings of a bong purpose likewise to those of a laboratory gas washing bottle. This "filtration" can guide to the faith that bongs are fewer harmful than other smoking methods.

though, a 2000 NORML-MAPS learn establish that "water pipes sift out more psychoactive THC than they do other tars, thus requiring users to smoke more to reach their preferred effect". In the learn, smoke from cannabis complete by the NIDA was haggard through a figure of smoking devices and analyzed. An inhalation machine, adjusted to mimic the puff length of cannabis smokers, drew smoke through a normal bong, a small moveable bong with a failure stem, a bong with a mechanical paddle that methodically mixes the smoke with the irrigate and two dissimilar types of vaporizers. Comparisons to customary non-filtered smoking methods were not built-in in these experiments.