An evaporative cooler is really just a large fan that blows air through water soaked pads producing a cooling affect. The fan pulls hot outside air through the pads and into the cooler and blows the cooled air out.Evaporative Cooler Pads. The Evaporative Coolers pads are most commonly made of wood shavings.n evaporative cooler is really just a large fan that blows air through water soaked pads producing a cooling affect. The fan pulls hot outside air through the pads and into the cooler and blows the cooled air out.