Prescription Treatments PT 221L Residual Aerosol - 17.5 oz. can Lambda Cyhalothrin 0.05% 221L Residual Insecticide can be used in and around the following locations; Apartments, Campgrounds, food Storage Areas, Homes, Hospitals, Hotels, Meat Packing and Food Processing Plants, Motels, Nursing Homes, Resorts, Restaurants, Schools, Supermarkets, Transportation Equipment, Utilities, Warehouses and Other Commercial and Industrial Buildings. 221L Residual Insecticide can be used in and around the following locations; Apartments Campgrounds food Storage Areas Homes Hospitals Hotels and more.