No, but they should make sure the people they hire are able to do their job properly.
But don't you think that in order to do their job properly, which may including saving people, they should have to be physically fit (weight requirement) and large enough (height requirement)?
Weight and height don't always factor in to to jobs such as fire and police work. If they are small enough but can do the job (be able to lift a certain amount, etc.) why should they be stopped from having the job even if they are smaller?
But is it really reasonable to think a 5'1, 120 lb women, could carry a 6'3, 300 lb man out of a building? How do you simulate that completely?
Most can't, some can. I realize that not many people will be able to do it but as I'm saying, why ban the people who can do it from the job? And the answer is there is no reason.