Great news! A good chemical-free way to prevent mosquitoes from bothering you when sitting outside is to just set up a fan nearby and turn it on. Mosquitos are weak flyers and this will keep them away.
The head guy in the fight against mosquitos and West Nile Virus in NYC (Dr. Bajwa, a medical entomologist) turns on a pedestal fan when sitting outside his home. No chemicals needed!
Bottom line: Using a fan can ward off mosquitoes. People differ in the types of fans they like to use (oscillating fan, stationary fan, ceiling fan). By the way, a breezy or windy day is also great in keeping mosquitos away.
From the NY Times: In a Decaying Queens Fortress, It’s One Man Versus 47 Kinds of Mosquito
He has his own method of dealing with mosquitoes. “When I find myself relaxing in my backyard, I always set up a pedestal fan,” he wrote. “Mosquitoes happen to be weak fliers, unable to contend with even a gentle breeze.” When he does get bitten, he added, “I make a conscious effort not to give in to the temptation of scratching.”
The NY Times wrote about this method already back in 2010: The Claim: To Repel Mosquitoes, Use a House Fan
The battle against mosquitoes is often fought with chemical repellents. DEET, the most popular choice, is highly effective, but it can be toxic, smelly and irritating.
For those who prefer a chemical-free repellant, a plain and simple house fan just might do the trick.
Studies have found that wind is an effective method against mosquitoes and other airborne pests. The reason seems obvious: it prevents them from circling and landing on you, like a windstorm keeping a plane from its descent. But that is not entirely the case. A fan dilutes and disperses the carbon dioxide you exhale. Carbon dioxide is one of the major chemicals that attract mosquitoes. The wind from a fan also cools you off. Sweat, lactic acid and body heat attract mosquitoes - factors that a fan can help minimize.
In one study in 2003, entomologists at Michigan State University used traps set up in a wetland by the C.D.C. to attract mosquitoes. Releasing carbon dioxide attracted more pests to the trap, and the more carbon dioxide, the more mosquitoes. Using fan-generated wind of various speeds helped keep them away.
“We recommend that fan-generated wind should be pursued as a practical means of protecting humans or pets from mosquitoes in the backyard setting,” they wrote.