Q: Does an electrical closet under 144 square inches need a sprinkler head?
A: The answer depends on your facility occupancy type and the requirements associated with that. If your facility is a hospital and the area in question was constructed prior to 1991, and there has not been any major renovation in the area, and the Construction Type does not require sprinklers, then there is no Life Safety Code condition that would require sprinklers in a small closet. However, if the Construction Type requires sprinklers (see 220.127.116.11 of the 2000 LSC) then sprinklers would have to be installed. If you conducted renovation in the area of the small closet since 1991, then sprinklers would have to be installed.
If your facility is a long-term care/nursing home facility, then the closet would have to be sprinklered. CMS has issued a memo that requires all nursing homes to be 100% protected with sprinklers, and a 12 inch x 12 inch closet would be included in this requirement to be protected with sprinklers.
If your facility is an ambulatory health care occupancy or a business occupancy, then sprinklers are not mandatory.
Also, please check with your state and local authorities to see if they have specific requirements for sprinklers.