A fire-rated door is a door that has been designed to withstand a certain degree of extreme heat per hour. Fire doors are the most common fire-rated doors. When people talk about the fire rating of a door, they are most often referring to the strength of a fire door. Different safety agencies, such as the Office of Compliance Safety and Health, measure how efficiently a door can maintain its integrity during a fire emergency. A high fire rating means that the door can withstand fires for long periods of time. If you are concerned about the fire rating of a door, there are several steps you can take to assuage your fears.
Make sure the door is a fire door and not an emergency door. Emergency doors are wired to alarm systems. Fire doors can be used for casual purposes but have a special use during fires.
See if a louver is present on the door. Louvers are slats through which smoke can pass. They are usually on medium-level doors; lower level fire-rated doors usually do not have louvers.
Open the door completely so that all latches are exposed. Many markings and indicators may be exposed when you have the door open.
Investigate the areas between each door latch. A label should show what temperature the door can withstand; this is known as the temperature holding. Temperatures vary, but a door must at least have a temperature holding of 250 degrees Fahrenheit.
Measure the glass thickness. Not all fire doors will have a glass window. If the fire door does have a glass window, the glass must measure at least ¼ inch in thickness. If it does not, then the door does not meet the Housing and Urban Development's legal definition of a fire door.