This is part one of a three-part article about heated hand dryers.

Distributors and their customers are well aware of the role hand washing plays in preventing the spread of illness. But hand hygiene discussions often gloss over the importance of drying hands after washing them.

For many people the perception is that once hands are washed, they are germ-free; therefore, drying them is inconsequential. However, research indicates that wet or improperly dried hands — just like poorly washed hands — can further aid the spread of germs.

“If we’re studying cross-contamination between two surfaces, we know moisture plays a big role in transfer, so wet surfaces transfer more bacteria than dry surfaces,” says Donald W. Schaffner, professor of food microbiology at Rutgers University, New Brunswick, New Jersey. “At the end of the hand wash, the important thing is that people’s hands are physically dry, because that’s going to reduce cross-contamination.”

Jet-air hand dryers — those that rely on air traveling at speeds of up to 400 miles per hour to shear water off hands — are among the most popular on the market today. But as an alternative to jet-air dryers, many facilities have installed standard-speed, heated-air hand dryers in their restrooms that emit warm air to aid in evaporating moisture off the hands. And although some standard-speed hand dryers feature the option to run with non-heated air, most users still opt for models that emit warm air.

“I think people associate dryers with heat,” says Darrel Hicks, infection prevention consultant based in  St. Louis and author of “Infection Prevention for Dummies.” “Whether it’s your clothes dryer or your hair dryer ... everything you think of as being a dryer usually has heat associated with it.”

In addition to the expectation that dryers should emit warm air, end users believe — rightly so — that heated air will speed up the drying process, which in turn could promote compliance.

“If you’re looking at heated air versus ambient air, I think there could be a case for speeding up that drying process so that people don’t get frustrated with how long it’s taking,” says Hicks. “If it dries hands faster, then people are more inclined to stay there until they’re dry.”

According to Schaffner, however, there are also other factors at play that will influence dry times.

“I suspect warmer air would be more effective in speeding hand drying, but drying your hands on a humid day versus a dry day might make a difference,” he says. “Also people’s skin chemistry is going to make a difference, so there are a lot of factors to consider.”