The Department of Defense, specifically the Department of the Air Force, is seeking sources for the modernization of the D-21 Fire Alarm System at Ellsworth Air Force Base (AFB) in South Dakota. The project involves upgrading both hardware and software components of the D-21 system, which is critical for incident detection and management, and includes a Preventative Maintenance Inspection (PMI) visit six months post-upgrade to ensure system performance. Interested parties are invited to submit a capabilities package by January 10, 2026, to Joseph Mace at joseph.mace.3@us.af.mil, as this sources sought notice is intended for market analysis and does not constitute a procurement commitment. Responses should include company details, business size, and a statement of intent to bid, with no proposals or cost data required at this stage.