Traditionally, evaporative cooler pads consist of excelsior (wood wool) (aspen wood fiber) inside a containment net, but more modern materials, such as some plastics and melamine paper, are entering use as cooler-pad media. Wood absorbs some of the water, which allows the wood fibers to cool passing air to a lower temperature than some synthetic materials. The thickness of the padding media plays a large part in cooling efficiency, allowing longer air contact. For example, an eight-inch-thick pad with its increased surface area will be more efficient than a one-inch pad.
Now, most evaporative air coolers use cellulous pads. It is honeycomb frame paper. The paper is made of special poplar tree. Normal paper will corrupte in water, but this kind of poplar paper will always strong in many years. Among this kind of paper pads, 5090 type has highest evaporation efficient.
COCO-COOLER brand evaporative coolers all use high efficient 5090 type pads.