Is equipment with a brush motor prohibited in a mutiplace environment? When searching the NFPA 99, 2018 version I could not find anything specific about a brush motor in the hyperbaric environment.
Thank you for your question. The UHMS hyperbaric oxygen safety committee (SC) can provide information, guidance and an opinion; however, the ultimate responsibility for these types of questions lies with the medical director and safety director of your facility.
SC Reply: Regarding brushed motors in the multiplace environment.
Brushless DC motors do not spark as they do not have brushes (satisfies the intention of NFPA 99, 2018, 184.108.40.206.11 & 220.127.116.11.13). For this reason, they are considered to be safer, especially where contained in a pressure-proof housing, or purged so as not to allow oxygen-enriched air to enter. These are user-specific decisions, based on risk assessment & mitigation. In short, we see brushless DC motors in purged housings being used.
The SC is not aware of specific wording in regulation to this effect as it could lead to misunderstandings as to what is safe. It is only safe if the risk is identified & understood, and mitigated.
The requirement for motors is stated in NFPA 99 as follows:
18.104.22.168.13 Exposed Live Electrical Parts.
No exposed live electrical parts shall be permitted, except as specified in 22.214.171.124.13.1 and 126.96.36.199.13.2.
188.8.131.52.13.1 Exposed live electrical parts that are intrinsically safe shall be permitted.
184.108.40.206.13.2 Exposed live electrical parts that constitute patient monitoring leads, which are part of electromedical equipment, shall be permitted, provided that they
meet the requirements of 220.127.116.11.17.
Motors located in the chamber and that are not a component of medical equipment shall meet one of the following requirements:
(1) They shall comply with 501.125(A)(1) of NFPA 70.
(2) They shall be totally enclosed in accordance with 501.125(A)(2) or 501.125(A)(3) of NFPA 70.
18.104.22.168.17 Portable Patient Care–Related Electrical Appliances.
22.214.171.124.17.1 The appliance shall be designed, constructed, inspected, and maintained in accordance with Chapter 10.
Referring to the NEC (NFPA 70), 2014 (draft version):
501.125 Motors and Generators.
(A) Class I, Division 1. In Class I, Division 1 locations, motors, generators, and other rotating electrical machinery shall be one of the following:
(1) Identified for Class I, Division 1 locations
(2) Of the totally enclosed type supplied with positive pressure ventilation from a source of clean air with discharge to a safe area, so arranged to prevent energizing of the machine until ventilation has been established and the enclosure has been purged with at least 10 volumes of air, and also arranged to automatically de-energize the equipment when the air supply fails
(3) Of the totally enclosed inert gas-filled type supplied with a suitable reliable source of inert gas for pressurizing the enclosure, with devices provided to ensure a positive pressure in the enclosure and arranged to automatically de-energize the equipment when the gas supply fails.
One can also refer to the NFPA 99, 2018 section on switches (which is what the brushes in a DC electric motor do):
Switches in the fixed wiring installation shall be waterproof.
126.96.36.199.11.1* Switch make and break contacts shall be housed in the electrical enclosure so that no sparks from arcing contacts can reach the chamber environment.
Neither the Undersea and Hyperbaric Medical Society (UHMS) staff nor its members can provide medical diagnoses or recommendations for equipment over the internet. The responsibility for medical diagnoses and treatments resides with the medical director; approving the use of equipment resides with the physician and safety director of the facility. Information provided on this forum is for general educational purposes only.