Are you allowed to have a water mist fire extinguisher in an operating room (OR) even though it isn’t rated for Class B fires?

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An organization is expected to determine and select an appropriate fire extinguisher based on a risk assessment. Operating rooms (ORs) usually have Class A fuels which are paper, drapes, and human tissue. Class B fires in an OR are flammable liquids that are typically limited to skin prep products and Class C fires are electrical equipment.

NFPA 99 states a water-mist or clean agent fire extinguisher can be used in surgery. Also, NFPA 99 allows the carbon dioxide (CO2) extinguisher, which is a type of clean agent. However, when CO2 is discharged, it is about -75 F, which can cause damage to tissue and as a result, many hospitals opt to exclude CO2 extinguishers. The primary reason for a water-mist or clean agent extinguisher is to prevent dry-chemical extinguishers from being present in the OR due to the elevated infection control risk of the fine powder if discharged in a surgical site. In fact, NFPA 99 2021 edition actually states that “Clean agent or water mist-type fire extinguisher shall be provided in operating rooms.” Further, when exploring Annex A of NFPA 99 2021 edition it’s clear the focus is on Class A fires. ECRI (Emergency Care Research Institute) recommends that a 5 lb. carbon dioxide extinguisher be available for protecting patients and staff. ECRI also does not recommend a water-mist fire extinguisher in the surgery environment due to infection prevention issues if patient wounds are open at the surgery site. It’s also important to understand that water-mist extinguishers only carry a rating for Class A and C fires.

Ultimately, yes, per code you are allowed to have a water-mist extinguisher but it’s important to remember that code is a minimum and there are many varying factors. In this case, a better approach might be to perform a risk assessment with a multi-disciplinary team to understand the quantity of flammable liquids and possible infection risk based on the type of surgeries performed in the operating room. This risk assessment would then drive the best direction forward.

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