PREVIS₂-OS is an acronym that represents the fireground tactical priorities of Perimeter, Rescue, Exterior Attack,Ventilation, Interior Attack, and Search (primary and secondary) with Overhaul and Salvage as supporting, complimentary tactics that are accomplished when appropriate (i.e., overhaul after attack). These tactical priorities are accomplished in the order that they appear in the acronym by the first-in company. This tactical priority model provides a more effective way to firefight in today’s faster moving, more toxic, and less forgiving fireground than those of the past.

PREVIS₂-OS is based off of the REVAS^1,2 tactical priority model developed in the 1980s, which emphasizes (and recognizes the importance of) venting structures prior to interior attacks. The REVAS acronym represents the tactical priorities of Rescue, Exposures, Ventilation, Attack, and Salvage.

The REVAS model was an upgrade from the RECEO model developed by Chief Lloyd Layman in the 1950s. RECEO was the foundation for Layman’s book Fire Fighting Tactics, published in 1953. His tactical priorities of Rescue, Exposures, Confinement, Extinguish, and Overhaul (with Salvage and Ventilation as a support function) were innovative for their time but were developed when a 2 × 4 was truly 2 × 4 inches, cut-and-stack framing still existed, and interior furnishings were still primarily made from natural materials. Back then, it was not uncommon for multiple fire companies to respond with five- or even six-person companies!