This little matter always leads to an energetic discussion during our Emergency Response assessments/planning exercises. But most states have a state code that will read something like this…
Access to refrigeration systems having a refrigerant circuit containing more than 220 pounds (100 kg) of Group A1 or 30 pounds (14 kg) of any other group refrigerant shall be provided for the fire department at all times as required by the fire code official.
Officially, the language above is from the IFC Section 605.5 Access (2012 – present) and most states have adopted this verbatim or in some other form. This requirement was put in the code to allow the local FD access for planning, inspection, and response. If the process is covered 24/7/365 by a capable person who can grant access and answer questions then nothing special is needed. However, if the process is left unoccupied for any period of time, the facility may need to either provide a key/password to the engine room or arrange for a Knox Box like the one shown below.
This is in NO WAY an endorsement of any commercial product or an attempt to make you purchase any product, but these devices have been around for decades and they work extremely well – much better than giving the FD a key or passcode.
The local FD will almost never access your facility without your knowledge, except during an emergency and no one is available to grant them access to the area of the emergency.