What Is a CO2 Trap and How Does It Work for No-See-Ums? | Biting Midge Basics

A CO2 trap releases carbon dioxide to mimic exhaled breath, drawing host-seeking biting insects toward a fan or sticky surface that captures them; for no-see-ums it works as a supplemental lure, not a cure.

The device only performs when the gas plume, placement, and airflow all line up. Biting midges are tiny enough to slip through standard window screens, and their bites leave welts that itch for days. Understanding what the hardware does — and can’t do — saves you from buying the wrong unit or expecting one device to empty a yard.

How Does a CO2 Trap Attract No-See-Ums?

Carbon dioxide is the primary long-range cue that draws blood-feeding insects toward a host, and the University of Florida IFAS notes that both mosquitoes and no-see-ums are highly attracted to CO2. The trap mimics that plume, then adds a second layer — airflow, warmth, light, or a chemical lure — to close the deal.

Commercial units release gas via a compressed cylinder, a small cartridge, or a propane burner that produces CO2 as it runs. A fan typically pulls approaching insects into a collection bag or cup once they reach the intake. Some models pair the gas with species-specific scents; Biogents, for example, combines CO2 with its BG-Sweetscent lure and says the gas broadens attraction to additional biting mosquito species.

The honest limit: manufacturer claims and published evidence are stronger for mosquitoes than for no-see-ums specifically. Treat any CO2 device as one tool in a layered approach, not an eradication machine.

What Do CO2 Traps Cost and How Much Power Do They Draw?

Prices span from under $50 for a light-and-fan indoor unit to several hundred dollars for outdoor models built around a gas system. Power draw is modest across the board, which matters if you plan to run a unit all season.

The Biogents Solo package ships with one trap, a 12-V outdoor power supply, two catch bags, funnel nets, a BG-Sweetscent lure rated for two months, a CO2 emitter nozzle, regulator, and extension tube. The Duo doubles the hardware and adds 33-foot cords and a Y-connector for splitting one gas source. The John W. Hock Model 1012.CO2 is a sampling instrument rather than a backyard product; its regulator meters flow at 100–500 mL per minute, and the manufacturer specs a 6-volt, 12-amp-hour battery for roughly one 24-hour day.

For readers who want to compare backyard-rated units side by side before spending, our tested CO2 trap roundup for no-see-ums breaks down what actually held up in the field.

Can You Build a CO2 Trap at Home?

Yes — fermentation produces a slow CO2 plume with kitchen supplies, and the University of Florida IFAS publishes a working design. Cut a 2-liter plastic bottle into a funnel shape, invert the top into the base, and bait it with 1 cup water, ¼ cup sugar, and 1 gram brewer’s yeast.

1. Use non-chlorinated or previously boiled water — chlorine suppresses the yeast.
2. Stir until the sugar dissolves, then add the yeast last.
3. Wait several hours; fermentation releases CO2 once bubbling begins.
4. Refresh the yeast and sugar when bubbling stops, or the trap goes inert.
5. Wrap the bottle in black tape or paint if you want to boost attraction.

The device works indoors or hung wherever the biting happens. Expect a modest catch — this is a lure, not a barrier.

Where Should a CO2 Trap Go, and What Goes Wrong?

Placement decides more of the outcome than the brand name on the box. Put the trap between the insects and the people, never beside the people you’re protecting — your own body emits CO2, heat, and skin odor that outcompete the device.

Common failures repeat: chlorinated water kills the yeast in a DIY build; a fermentation mix that stopped bubbling is no longer emitting gas; an indoor-rated trap won’t help when midges breed outside and fly in; and a single unit will not clear an established infestation.

CO2 traps do not touch breeding habitat. Standing water, damp organic material, dense vegetation, and animal-associated sites all need separate management. Compressed-cylinder models also require the correct regulator, secure upright storage, and ventilation — never improvise a connection or mix pressure fittings. Model specs here are US-market units; Biogents’ Mosquitaire Guardian CO2 page lists NEMA 1 / Type A 12-V outdoor power supplies, so verify your outlet setup before buying.