Thoroughly awful bit of kit, not well suited to field conditions.
Once lived and flew in mine for 3 days in the early 80s during a deployed site field trial, in the European summer heat. We were given short breaks in a shelter to ablute and eat but apart from that, we were constantly kitted up, always dripping wet with sweat. No help was given with moving our full personal deployment kit to and from the aircraft each time we flew, which I remember as the one thing that really p1$$ed me off the most!
My crewman and I were required to sleep wearing it, as best as we could. I remember being required to plan, brief and lead a 4 ship early morning task wearing full kit, having slept in simulated contaminated conditions, which was an interesting experience to say the least, not least the actual difficulty of communicating verbally outside of the aircraft.
The worst part about sleeping in it was that despite using a head harness, the mask moved off the face unless you slept flat on your back, allowing cold air to blow straight in your eyes. My colleague woke up at midnight, screamed, pulled off his still hissing AR5 and threw it on the straw (we were sleeping in a barn hayloft under the watchful eye of trials team staff). He rubbed his eyes, uttered a few choice expletives, then re-donned it, fastened up the head harness and went back to sleep. The following morning he couldn't remember anything about it! He was deemed "a casualty".
At Endex, on finally getting home and undressed to have a shower I found I was covered from neck to foot in ingrained charcoal from the undersuits.
No doubt everyone would be very glad to see the AR5 gone!