I have to admit that I can't offer much in the way of specifics in this area, however, I would like to suggest something you might want to consider. I imaging the fire marshall is describing how he interprets some "codes" dealing with this issue. I would request the specific local/state/ and federal codes/regulations that he using to justify these requirements. I'm sure they are based on his interpretation (which I am not advocating may be wrong in any way), and by reviewing them yourself may shed some light. For instance, in another ASTM standard we deal with in another field, one statement is that the building should remain at "service conditions" however, the method of maintaining those "service conditions" are not defined. So perhaps "central heat and air" is not specifically required, but more just certain ambient conditions? If you have the codes in hand, it would be helpful in trying to work with the fire marshall on compromises in adjustments to maintain compliance with the "codes"