Build a simple evaporative cooler

If you live in a genuinely dry climate, moving air through a wet evaporative pad can cool the incoming air while using far less electricity than conventional air conditioning.

This is climate-specific. It is not a useful substitute for AC in humid weather. If the air is already humid, adding more moisture can make conditions worse.

What you need

A battery/USB fan or small box fan, a rigid container or frame, evaporative-cooler pad material, clean water, and a way to keep the pad wet without allowing water to reach the fan, wiring or battery.

Basic setup

1. Secure the wettable pad over an intake opening.
2. Wet the pad thoroughly but do not leave water where it can contact electrical parts.
3. Position the fan so it pulls or pushes outside/dry air through the wet pad.
4. Give the moist air somewhere to exit. Evaporative cooling works with airflow through the space, not a sealed room.
5. Re-wet the pad as needed and keep the pad and reservoir clean.

Important: This is supplemental cooling, not life-safety air conditioning. During dangerous heat, use water-based body cooling and relocate to an air-conditioned place when possible. Do not depend on a fan alone when indoor temperatures are dangerously high.

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