I received an email from a teacher asking how long it is safe to listen to a school fire alarm. She knew that fire alarms are designed to be very loud to prompt an immediate evacuation, so the exposure time would usually be limited. However, due to the unfortunate frequency of school shootings, schools now use fire alarms to communicate dangerous situations, so the emergency protocol when hearing a fire alarm is not to evacuate, but instead to “hold and wait” or shelter in place inside the building.
This longer exposure time than anticipated by NFPA 72, National Fire Alarm and Signaling Code, created a concern about hearing damage. Her principal distributed ear plugs, but the teacher was not convinced that was an effective solution.
I think that the noise exposure does not come close to what OSHA 1910.95(a) - Occupational noise exposure describes, which is referenced in the code. I advised her to review the situation based on the sound level and exposure time.
Typically, a fire alarm audible appliance, such as a horn, produces approximately 90 dBA. Generally, there are no horns in a classroom. The dBA output of horns in the hallway is affected by walls, doors and distance from the classroom, which reduces the noise level by 20–30 dBA at a minimum. So based on the OSHA information, students and teachers could stay in their classrooms with no hearing protection for at least 8 hours with no hearing damage.
Ear plugs would reduce the noise level and their ability to hear safety instructions during an emergency.
Improper use of alarm systems
I was unaware of this misuse of schools’ fire alarm systems and asked why it was a practice to leave the fire alarm operating and not evacuate. I assumed this was a one-off situation until I was given a sampling of school district requirements.
The horns should not be used as the teacher describes. If administrators continue to misuse the fire alarm system, they are creating liability issues and should reevaluate their policies. I would recommend using a constant tone for evacuation and a coded temporal pattern for another emergency. The coded signal should be limited to a smaller time, such as 15 minutes.
Districts’ changing requirements
Many schools have changed fire alarm protocols after recent school shootings. It used to be that if a fire alarm sounded, students evacuated immediately. That’s no longer the case in an increasing number of districts.
When an unscheduled fire alarm occurs at Hartford High School and Hartford Middle School in Van Buren County, Mich., the students shelter in their classrooms while administrators investigate. The school officials call police, attempt to pinpoint which alarm sounded, check security cameras to see who or what activated the alarm and walk the halls and grounds looking for any suspicious activity.
To mitigate the possibility of an assailant using manual fire alarm boxes as part of an assault, the Colorado Division of Fire Prevention and Control emphasizes that many schools with existing fire alarm systems may be able to eliminate most of them. These schools must meet at least one of the following criteria based on provisions in the 2015 International Fire Code:
1. Manual fire alarm boxes are not required in Group E occupancies where all the following apply:
1.1. Interior corridors are protected by smoke detectors.
1.2. Auditoriums, cafeterias, gymnasiums, and similar areas are protected by heat detectors or other approved detection devices.
1.3. Shops and laboratories involving dusts or vapors are protected by heat detectors or other approved detection devices.
1.4. Off-premises monitoring is provided.
1.5. Manual activation is provided from a normally occupied location.
1.6. A means is provided to communicate from the normally occupied location to other areas within the facility.
2. Manual fire alarm boxes shall not be required in Group E occupancies where all of the following apply:
2.1. The building is equipped throughout with an approved automatic sprinkler system installed in accordance with Section 903.3.1.1 [of the IFC-2015].
2.2. The fire alarm system will activate on sprinkler water flow.
2.3. Manual activation is provided from a normally occupied location.
I believe notification appliance loudness is not an issue. I am more concerned with the changes to the fire alarm system response in schools.
Given this new information, ensure school districts are not making changes without your input and assistance, and make sure the changes still comply with the applicable codes.