Ideally, moisture does not linger for more than 20 minutes after we have showered, or it can start leaving long-lasting damage. The bathroom becomes a breeding ground for mildew, mold, steam and odors. Only a shower exhaust fan can stop this from happening by forcing air out, such as to the garage, in order to eliminate moisture as fast as possible, similar to a computer exhaust fan removing heated air brought on by dust.
Recognized brands like Air King, Breidert, Broan, Fantech, NuTone and Panasonic offer a wide selection of shower exhaust fan, often ceiling, interior wall, exterior wall or inline mounted. Dual grille, single grille, passive inlet vents, one-vent, 2-speed and ductless exhaust fans, along with combination fan/heat models, are popular and may come with or without a warm light and/or night light for space efficiency.
Double grille fans are best suited to vast spa-like shower baths that are a current trend in luxury baths. They provide spot ventilation at the source, using a remotely mounted fan motor for distributing air in several bathroom areas at a time. Single grille fans are most fit for compact shower baths, vanity and powder rooms. The small-scale grille is ceiling-mounted separate from the fan motor remotely mounted away from the actual living space.
A good choice of shower exhaust fan is Energy Star qualified, with enhanced CFM to watt efficacy to increase energy savings. It should function noiselessly such as with blade rotation at lower speeds and be made durable such as with rust-resistant stainless steel parts that operate without overheating.