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.
“While we’ll continue to take action where we see the rules being broken, the nature of some of the businesses behind these ads means enforcement alone isn’t enough to stop the problem,” said the ASA.
Although the watchdog regulates paid-for adverts on platforms including YouTube and Facebook, it cannot issue fines itself.