Hmm, metal fires are very nasty. Venting atmospheres is actually wortwhile in this case. I imagine that emergency services will have first line bots placed in many places, bursting out of their cupboards when needed. Imagine a walking fire extinguisher, linked to the emergency service tacnet. If there is a fire they will rush to it and start working. If things are more serious other tools can be used: Asphyxiant nanoswarms can be really effective in some situations. Imagine respirocytes, but sucking up oxygen. Other kinds of nanoswarms can block oxygen inputs, patch leaks or prevent spread of the fire. Emergency services can likely take control over nearby bots and use them to save people or do necessary interventions. Flooding compartments with inert gases might be entirely feasible, especially since even biomorphs are fairly tough - a bit of asphyxiation is not too bad if you get plonked into a healing vat directly afterwards. Real rescue workers have tough synthmorph shells and built-in equipment for getting around. In a martian environment the issue is often less fire and more quickly repairing big leaks. But since these services need to deal with anything, the workers also have anti-nano and anti-bio protection. I can imagine them like a "civilian" reaper morph, with the guns replaced with hoses that can spray various liquids, gases and nanoswarms.