A quick note on the balaclava thing. We are required (My department) to wear them if we are going to deploy a Light Sound Diversionary Device (LSDD- Liability speak for Flash-Bang). They are made of Nomex and they are required as a piece of safety gear. Do some hide behind them? I'm sure they do. We normally pull ours off as soon as the location is secure while we wait for the case agent. FWIW we don't wear ski masks.