Swamp Coolers:
Types for Outdoor Use

An evaporative cooler, more commonly known as a swamp cooler or air cooler, can be used for outdoor cooling as long as it is set-up correctly and rated for safe use outdoors. Some are better for outdoor cooling than others.

Cabinet Configurations

Avoid styles that have air vents coming out the bottom of the unit. These are designed to be permanently mounted to the roof of a building with cool air vents leading from the unit down into the building.

Look instead for coolers with air vents coming out the side, or out of the top with air flow adapters than can direct the air flow where you need it. Also look for features such as wheels that can make them easier to move around and use on rough outdoors surfaces.

Swamp coolers are classified by how they work or by their size.

How Swamp Coolers Work


Single-stage are the most common and least expensive to purchase. They create more humidity than two-stage units — as much as 70 – 80% relative humidity. This means their cooling will be most effective in only the driest climates and weather.

Single-stage units with “direct” technology use the most basic technology: warm air blowing through the pads and the cooled air blowing directly out of the unit. These are the least expensive and easiest to find. Single-stage units with “indirect” technology add a heat exchange to the unit. This may lower the amount of humidity produced by the unit, but it can also lower the cooling somewhat.


A two-stage swamp cooler (also called “indirect-direct”) produces less humidity than a single-stage unit – around 50 – 70% relative humidity. But because of the way it’s made, this does not lower the cooling effect. In fact, the air from these can be up to 6°F / 3.5°C cooler than air from a direct cooler. These are more expensive than similar units that use direct cooling, and also require more maintenance. They are mostly available in larger units, but this technology is making its way down to smaller portable swamp coolers, too.

In the first (indirect) stage the warm air goes through a cooling chamber where it is pre-cooled. In the second (direct) stage this pre-cooled air blows through the water soaked pads and then into the area being cooled. Because the air going through the pads is already cooled a bit, it needs less moisture to lower it to the desired temperature. Since it picks up less moisture, it picks up less humidity to provide the same degree of cooling as a single-stage unit. Less humidity means it can cool in a wider range of weather conditions than a single-stage unit.

Another technology uses desiccants (materials such as silica) that remove moisture from the air. Fresh air first passes through this material to dehumidify it before going through the single-stage or two-stage cooling process.

Other Outdoor Cooling Methods

Swamp coolers combine two of the most effective outdoor cooling methods. But, as mentioned above, they have some limitations. You can maximize their cooling by combining them with other methods or devices, or other options may be more effective.

Take a look at our comparison page or our pages on other outdoor cooling methods:

  • Outdoor fans combine well with swamp coolers, ensuring adequate air flow and distributing the cool air from evaporation.
  • Misting fans are another kind of device that combines evaporation and wind chill to cool outdoor areas.
  • Outdoor shades are a nearly universal solution that work well with any outdoor cooling method, including swamp coolers.
  • Misting systems use a similar technology as swamp cooler, but in an open system that can cool larger areas.
  • Portable air conditioners are especially suited to enclosed areas (tents, sheds, etc.) and special circumstances.