Matthews said he bought several of the devices to see whether they performed as advertised.
The civil engineer and content creator said rather than buying something that would bring the temperature of his room down quickly, he found he had instead bought some “cheap components” made using “flawed science”.
One advert described the product as a “reverse-engineered aircon unit” featuring “a liquid-compressed cooling cartridge”.
Matthews said the device actually contained “a load of cardboard fins that get wet as the water blows past them”.
While so-called “swamp coolers” – machines that chill air by evaporating water – do work reasonably well in hot, dry climates, they also increase humidity and so are much less effective in humid places like much of the UK.
They are also not conventional air conditioners, which work by removing heat from a room via an exhaust hose or external unit.
“I really feel for the people that have been sucked into buying some of this rubbish,” Matthews said.
The ASA said it was monitoring sites to spot such adverts and issuing an enforcement notice “instructing advertisers to get their ads in order”. It also bans adverts found to have breached its rules.
Although the body regulates paid-for adverts on platforms including YouTube and Facebook, it cannot issue fines itself.