Air flow controllers helps to equally distribute the air into the test and thecontrol chambers at the rate between  40-400ml per minute. A knob is provided to set the required air flow. Varients that affects the choice of air flow controllers are 1. type of insects and its sizes 2. type of the flow meter i.e., 2 way, 3 way, or 4 way and the choice chamber size or the size of the insect release area  3. effectiveness of the testing chemical or plant parts. It means how strong is the ordor is? 4. For fine tuning the minimum amount of concentration of semio-chmical needed to initiate response from the insects