An air cooler, also known as an evaporative cooler, cools the air through the evaporation of water, while an air conditioner cools the air using refrigerants. Air coolers are generally less expensive and more energy-efficient than air conditioners but are less effective in humid climates and at cooling very large spaces.

An air cooler draws in warm air and passes it over water-soaked pads. As the water evaporates, it absorbs heat from the air, thus cooling it down. The cooler air is then circulated back into the room.

Air coolers can be suitable for people with allergies if they are equipped with filters and maintained regularly. The water in the air cooler should be changed frequently to prevent the growth of mold and bacteria, which can exacerbate allergic reactions.

Some air coolers are designed for outdoor use. However, it's crucial to ensure that the model you choose is appropriate for the environment, as direct sunlight and rain can damage the unit. Outdoor air coolers often come with protective covers and should be placed under shelter when not in use.

To maintain an air cooler, empty and refill the water tank regularly, replace or clean the water filters, and wash the pads according to the manufacturer's instructions. Store the cooler in a dry place during the off-season to prevent rust and deterioration.