HEPA filters used in BSCs for chemo (antineoplastic) drug preparation pose a chemical hazard as opposed to a biological hazard. Typically, BSCs are used for either biohazard or chemo drug work therefore mixing of these two types of hazards are rare. Chemo drugs can pose a variety of acute and chronic occupational exposure hazards. The current guideline document is published by OSHA: in Chapter 21 of their technical manual. When a HEPA filter is changed in a BSC used for chemo drugs, the old filter is classified as hazardous drug (HD) waste. It should be bagged in plastic, labeled, and disposed of as solid hazardous drug waste. Disposal of HD waste can be regulated by the EPA, state, and local toxic waste laws depending on the drugs used. It is important that the facility have in place a hazardous drug safety and health plan which would document how HD waste should be disposed.