WARNING: This video contains graphic footage. Spit hoods, or spit masks, are used by first responders across Canada to protect themselves from being spit on or bitten. But an investigation by CBC's the fifth estate and Radio-Canada's Enquête has found use of these devices is risky — and can be deadly. You can watch the full documentary at youtube.com/cbcfifth. »»» Subscribe to CBC News to watch more videos: http://bit.ly/1RreYWS For breaking news, video, audio and in-depth coverage: https://www.