How to Use a ShopVac to Blow Borax or Boric Acid Into Crawlspaces to Kill Roaches

Mix equal parts boric acid with sugar or flour. Stir the two together in a bowl.

Turn your ShopVac to the leaf-blowing setting. Not all ShopVacs can be used for this project because not all ShopVacs come equipped with the blowing feature. Make sure that you have or rent the correct ShopVac before trying to perform this procedure.

Put on a cleaning mask and protective eyewear.

Pour out a small amount of the boric acid mixture on the floor just inside the entrance of the crawlspace.

Turn on the ShopVac and blow the boric acid mixture into the crawlspace. The blow feature on a ShopVac is extremely strong, so you will only need to turn the machine on briefly so that the mixture is blown into the space.