Back when I was an EHS engineer for a manufacturing facility, a mezzanine was converted to work space for a small team of technicians. One day, their team leader told me the only door to their space opened to the Heat Treat area. In there were several furnaces that burned natural gas. The team leader was concerned that, in case of fire, they would have to exit through the area where the fire was raging. I agreed; an OSHA regulation does require an additional means of egress.
The back of the mezzanine had space for an emergency escape ladder. I found a supplier; it would cost about $2,000, not a lot of money for a large multinational company like ours. To my amazement, all managers thought this was an unnecessary waste of money. The plant had been operating the Heat Treat department for more than 20 years without incident.