A "mosquito magnet" is a kind of mosquito trap that aims to kill all the mosquitoes in a particular area. It essentially sets up a fake mammal for the mosquitoes to be attracted to and then vacuums them up. Mosquitoes can sense warmth, carbon dioxide (exhaled by mammals), and plant chemicals (produced by mammals that eat plants) or sweat chemicals. So to attract mosquitoes, a mosquito magnet needs to produce these three things.
Mosquito magnets use propane that is "burned" catalytically to produce carbon dioxide, heat and moisture. Using a catalyst instead of a flame cuts down on the risk of fire and doesn't produce other gases like carbon monoxide. In addition, a cartridge containing octenol (which stimulates plant chemicals) or Lurex (which stimulates sweat chemicals) is included in the mosquito magnet. Different types of mosquitoes are attracted to different chemicals. The mosquito magnet mixes the carbon dioxide and moisture with the chemical attractant and blows it out, creating a gas plume that attracts the mosquitoes. Then a vacuum, which is created by a fan, sucks the mosquitoes into a net where they eventually die.
Mosquito magnet-type traps can be extremely effective if they are put in the right place, set up properly and tuned to attract the species of mosquitoes that live in your area. In fact in just six days, six Mosquito Magnets managed to capture 1.5 million mosquitoes at one U.S. Coast Guard station in the Bahamas. Generally, though, a mosquito trap must be in place for between four and six weeks before it begins to have a significant effect. In this time, existing eggs hatch, the mosquitoes are captured, fewer eggs are laid and the mosquito population begins to decline.