Halon is not a nice thing to breath and it destroys the ozone layer. They should have phased them out ages ago. One of the alarms is to tell people the system is about to be deployed and you should get out of there.
Server rooms depress me.... I work in one that feels like the landing bay of the death star, the people who run it have the sense of humour of storm troupers. I am banned from taking anything into there other than ear plugs and my laptop. I am not even allowed ear phones anymore....