are presented in aerosol form application_number US 201113070744 A description one preferred embodiment of the invention is a formulation containing 0 6 pyrethrins 39 4 of isopar h an isoparaffinic hydrocarbon solvent and 60 of liquid petroleum gas such as a mixture of propane n butane and isobutane the pyrethin need not be presented in pyrethrum extract form a variety of other hydrocarbon solvents particularly isoparaffinic solvents such as isopar l or c and a variety of other known aerosol propellant gases can be used regardless of whether hydrocarbon based the primary intended use of these repellants are indoors such as in rooms that are about 30 m 3 in size of course the size of the room is not critical as the larger the room the more repellant used insect knockdown tests were conducted an indicator of insecticidal effect comparing formulations with and without significant synergist levels for example our product was tested as a composition with 0 9 pyrethin in isopar h versus a similar composition having pbo as well 100 mortality was achieved within 3 hours for both types of formulations against mosquitoes a repellency test was also conducted to examine a comparison of compounds having the synergist and not having the synergist the essential absence of the synergist did not cause a significant decrease in effectiveness surprisingly essentially deleting the synergist particularly when a majority of the particles of the formulation preferably 80 had 10 to 46 micron diameter d v 10 to d v 90 did not adversely impact repellency against mosquitoes while.