How to Build a Non-Toxic Box Fan Mosquito Trap for Your Yard

Here is a step-by-step tutorial on how to build a mosquito trap using a high-powered box fan, based directly on Dan Roas's experience. This method keeps your yard and pets bite-free without using harsh poisons.

• A high-powered box fan (the kind with a metal cage). The manufacturer will tell you not to get it wet, but Dan has had his running in the rain for 2-3 years without issue.
• A furnace filter or window screen (to cover the back of the fan).
• Rare earth magnets (to hold the screen in place). They will rust over time but still work.
• Rubbing alcohol (isopropyl alcohol).
• Water.
• A spray bottle.
• A bottle of seltzer water (or club soda). Dan uses this because he likes drinking flat seltzer, but dry ice would work even better.

1. Attach the screen to the back of the fan. This is the intake side. The screen does two things. First, it traps the mosquitoes. Second (and more importantly for the fan's lifespan), it blocks "gunk" like pollen, car exhaust pollution, and dust from getting inside the motor. That stuff will clog the grease in the bearings and kill the fan. The screen protects the fan.

1. Secure the screen with magnets. Use the rare earth magnets to hold the screen in place. It’s a simple, strong system that lets you swap out screens easily.

1. Mix your spray. In a spray bottle, mix rubbing alcohol with water at a 2:1 ratio (two parts alcohol to one part water).

1. Position the fan. If you have a pet that hangs out in the yard (like Dan's dog, Rocky), put one fan near them. This creates a "bubble" of moving air. Dan says Rocky never gets bit and never itches, even though he acts as a mosquito attractant. If you have a ditch or a known breeding ground, set a second fan up facing that direction.

1. Activate the CO2 trap. Open the top of the seltzer water bottle just enough to let the CO2 seep out. Place it in front of the fan. Mosquitoes are attracted to the carbon dioxide. The fan then sucks them into the screen. The seltzer trick works for about 3-4 hours. Dan notes you can drink the water afterward, though it won't taste great.

1. Spray the screen. When the screen fills up with bugs, spray it down with the rubbing alcohol mixture. The alcohol dries out and kills the mosquitoes instantly, but it evaporates completely. This is the key to the whole system.

This is the part Dan emphasizes. If you use poison, you kill the "cleanup crew." When you spray the alcohol, it kills the mosquitoes, but the alcohol evaporates. The ants, lizards, and frogs that come by for an easy meal don't get poisoned. They can then eat the dead mosquitoes off the screen.

Dan says after a night of catching around 3,000 mosquitoes, you’ll see the ants "ripping these guys apart." All they leave behind are mosquito legs. It’s a self-cleaning system.

• Fan longevity: The manufacturer will tell you not to let the fan get rained on. Dan has ignored this for years. The fans hold up, but if you live near a highway, the pollution buildup will eat through the steel. The screen helps a lot.
• Switches: As the fans get older and get rained on, the switches can seize up.
• Don't use poison. The whole point is to avoid it. The alcohol evaporates, leaving the beneficial bugs and animals safe to do their job.

This won't solve the world's mosquito problem, but for a backyard, a dog house, or a chicken coop, it works. No foggers, no DEET, just a fan, a screen, and some seltzer.