Mini USB Desk Air Cooler Fan

This is a personal cooler rather than a room appliance, and understanding that is the difference between being pleased with it and disappointed. It moves air across the space immediately in front of it, which is exactly what you want at a desk and nowhere near enough to change the temperature of a room.

The evaporative element works by passing air over a small water reservoir. Water absorbs heat as it evaporates, so the airflow arrives a little cooler and less dry than a plain fan's. That effect is real but modest, and it works best in dry air: in already humid conditions there is little evaporation to be had.

It runs from USB, so it works from a laptop, a plug adapter or a power bank. Empty the tank when it is not in use rather than leaving water standing, refill with clean water, and clean the reservoir regularly, since standing water in a warm room grows bacteria. Do not add ice, oils or scented liquids unless the manufacturer's instructions specifically permit it.

• Personal desk cooling, not a room appliance
• Evaporative element cools airflow modestly, best in dry air
• Runs from USB, laptop, adapter or power bank
• Empty the tank when not in use; clean it regularly
• Use clean water only unless instructions say otherwise