The Fogmaster 7401 ULV Machine changes liquid material into a fine mist which is so fine it is barely detectable by the human eye. ULV is a special type mist or fog which is comprised primarily of particles which are very small. These single digit micron sized particles in theory work better on flying insects and stay suspended longer than larger based aerosols which ordinary foggers produce. These machines are adjustable up to a couple of ounces a minute. However, don’t expect to get any type of heavy flow as you can from our other machines like the 6309 or 6308. The 7401 is a true ULV machine which means just that: Ultra Low Volume.