There is no powder left behind after using the CB PCO Fogger with Pyrethrins, it will dissipate in the air after use.  All pets and people must leave the home while the fogger is being used and they must remain out of the home for about 2 hours. The home should then be vented by opening the windows and doors for about 30 minutes. After this time period it will be safe for people and pets to return to the home.