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#101Wednesdays: Regarding fire doors, what rating do I need?

Blog Post created by gharrington Employee on Jan 24, 2018

 

When I’m asked, “What is the required rating for a door in a particular wall?” nine times out of 10 my answer is, “It depends.” (This is the standard answer for nearly everything code-related.) In the Life Safety Code, required ratings for doors and other opening protectives (e.g., windows) depend on the required hourly, fire-resistance rating of the barrier in which the opening is located and the function the barrier is serving.

Not all fire barriers are created equal. A door in an exit enclosure fire barrier will probably require a different rating than a door in a similarly rated corridor or hazardous area enclosure. Or a smoke barrier. Or a smoke partition. Or a shaft enclosure. (You get the idea.) At first glance it may seem convoluted, but the code does a good job of consolidating the opening protective rating requirements in one location. In the 2018 edition, you’ll find the required door rating in Table 8.3.3.2.2 (what I’ll refer to as “the table”). In the 2015 and earlier editions, the required ratings were located in Table 8.3.4.2. Prior to the 2003 edition, there was no handy consolidated table. If you’re using the 2000 or earlier edition, you’ll have to sort through a series of requirements and exceptions to determine the required door rating. (If you’re using the 2000 or earlier edition, you’re using a code that’s some 20 years out of date, and it might be time to join the rest of us in the 21st century. But I digress.)

To use the table, you’ll first need to establish the fire barrier’s purpose as required by the code. The table lists the purpose under the heading “Component.” Components include:

  • Elevator hoistways
  • Elevator lobbies
  • Vertical shafts
  • Horizontal exits
  • Exit access corridors
  • Other fire barriers
  • Smoke barriers
  • Smoke partitions

This is where the table has, at times, caused some confusion. Some have misinterpreted it as prescribing minimum fire-resistance ratings for various fire barriers. For example, the bottom row addresses smoke partitions. The second column specifies fire-resistance ratings for smoke partitions (half hour and one hour). Some have been led to believe that based on the table, all smoke partitions must have a minimum fire resistance rating of a half hour. This is not the case for smoke partitions or any of the other components listed in the table.

The requirements for smoke partitions are located in Section 8.4; you’ll find no fire-resistance rating requirement there. Smoke partitions require a rating only where required by another section of the code. An example would be corridor walls in new, large, residential board-and-care occupancies, which require a half-hour rating (32.3.3.6.2). Once it’s determined that the smoke partition requires a fire-resistance rating, then refer to the table to determine the required fire-protection rating of any doors. In the case of a half-hour rated smoke partition, doors must have a one-third hour, or 20 minute, fire-protection rating. In short, use the table to determine the required opening protective rating when a barrier is required by another section of the code to have a fire-resistance rating.

Fire barriers having a one-hour rating might require one-hour doors, three-quarter-hour doors, or one-third-hour doors. Again, it depends on the barrier’s application. Fire barriers having a two-hour rating generally require one-and-a-half hour doors. Fire barriers with a rating exceeding two hours are rarely required by the code, except for a few occupancy separation fire barriers involving relatively hazardous occupancies.

I sometimes get the question, “Why does the code allow a 20-minute door in a one-hour barrier? Why not just require a one-hour door?” This would certainly make life easier when applying the code, but it also might require a more expensive door than is actually needed for life safety. Where the code requires 20-minute doors, it’s usually in a barrier that the committees primarily wanted to be smoke resistant. Before the days of smoke partitions, which first appeared in the 2000 edition, when a committee wanted a smoke resistant barrier (e.g., a corridor wall), it was simpler to mandate a one-hour barrier than to come up with criteria to evaluate smoke resistance. Since they really wanted a nominal degree of fire resistance, rather than mandating a substantial one-hour door, they were comfortable with a 20-minute door, which would inherently resist the passage of smoke.

Other reasons for the difference in fire barrier ratings and door ratings are the tests used to establish the ratings. You might have noticed I refer to the fire-resistance rating of a fire barrier, whereas a door has a fire-protection rating. Fire barrier assemblies are tested at a lab using a standard like ASTM E119, Standard Test Methods for Fire Tests of Building Construction and Materials, which yields a fire-resistance rating. Fire doors are tested using a standard like NFPA 252, Standard Methods of Fire Tests of Door Assemblies, which yields a fire-protection rating. Comparing the ratings from the different tests is not an apples-to-apples comparison. An hour’s worth of fire resistance (fire barrier) is not necessarily equivalent to an hour’s worth of fire protection (fire door).

And although it’s not a very scientific reason, this is the way the code has done it for many years and it seems to work. To this point, there has been no compelling reason to change the approach. If it’s not broken, there’s no need to fix it.

For more details on fire door installation, inspection, testing, and maintenance, check out NFPA 80, Standard for Fire Doors and Other Opening Protectives. NFPA also offers online training for NFPA 80 ITM requirements and classroom training on NFPA 101 and NFPA 80 fire door inspection for health care facilities.

Thanks for reading, and as always, stay safe.

Got an idea for a topic for a future #101Wednesdays? Post it in the comments below – I’d love to hear your suggestions!

Did you know NFPA 101 is available to review online for free? Head over to www.nfpa.org/101 and click on “Free Access.”

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