Omae, they're not in the personal protection racket. It's not meant to take a missile. The Sentinel is a room fighter, with the Barret added on as an afterthought so that it wouldn't be totally defenseless out in the open. The Sentinel comes with a nifty little invention that filters it's exhaust until it only spews out clean air. Admittedly these filters have to be changed every couple hours, or your 5 Million nuyen piece of hardware suddenly becomes a Five million nuyen paperweight.
Some places forgoe the filters altogether.
Some have powerful ventilation systems to deal with the smoke, and other places use the smoke as added security. Any place personnel are essential is airtight with an oxygen reserve, people only go through places the Sentinel patrols wearing oxygen masks. It's amazing, no one has picked up on how physically powerful this thing is. It carries more weight than any other anthroform could. Only the scientists who worked on the project know how this is possible.