ULV Cold Fogger

Overview

A ULV (ultra-low-volume) cold fogger is a pesticide application tool that converts liquid formulations into a fine aerosol mist for spray coverage of crops, buildings, and large outdoor areas. Unlike thermal fogging equipment, which heats and evaporates the formulation, cold fogging relies on mechanical shear: a high-speed blower jet (150–200 km/h) atomizes the liquid as it is injected into the airstream, creating droplets of 5–15 micrometers that remain suspended and drift with the air.

The equipment consists of a small gasoline engine coupled to a centrifugal blower, a metering pump that injects pesticide formulation into the jet, a liquid reservoir, and an intake filter. The operator holds the nozzle and aims the spray jet across crops or structures. By adjusting throttle and flow rate, the user controls both application volume and coverage density without stopping the machine.

How it works

The Gasoline Engine, typically a single-cylinder 25–40 cc two-stroke or four-stroke, runs at 5000–8000 rpm and drives the Motor and Drive coupling. A Drive Belt transmits power to the Blower Assembly, which spins at high speed to accelerate ambient air through its Blower Fan to velocities of 150–200 km/h. The air exits the Blower Housing as a high-velocity jet directed toward the spray nozzle.

Simultaneously, the Metering Pump draws liquid from the Liquid Tank and pressurizes it to 10–30 bar. The Needle Valve in the Flow Control System system allows manual adjustment of the pump output, controlling the application rate. The pressurized formulation is metered through the Nozzle Block to multiple Spray Nozzles, where it is injected tangentially or axially into the blower jet. The high-velocity air shears the liquid into a fine mist as it exits.

The droplets are small enough (5–15 µm) to remain airborne and suspended in the air, drifting with the wind to cover plant canopies or structural surfaces. The Pressure Relief Valve valve protects the system from overpressure, and a Check Valve prevents back-siphon when the pump stops. Optional Solenoid On/Off Valve allows hands-free on/off control via an electrical switch or proportional valve for variable-rate application.

Air intake flows through the Air Intake System system, which includes the Intake Filter Element to prevent dust and debris from fouling the blower impeller. The Fuel System supplies the engine with gasoline, and the Control System allow the operator to adjust throttle speed, metering rate, and spray start/stop.

Use and efficiency

ULV fogging is efficient because the small droplet size maximizes surface coverage and reduces formulation volume required compared to conventional high-volume spraying. A hectare might be treated with 5–20 L of spray mix instead of 200–400 L. The trade-off is that wind conditions, droplet drift, and accurate timing become critical; fogging must occur during low-wind periods to prevent off-target drift or poor coverage.

Cold fogging is preferred in controlled-environment applications (greenhouses, storage facilities, livestock shelters) and for adult mosquito, midge, and fly control in large outdoor areas. It avoids the heat and smell of thermal fogging and is safer to handle during operation.