The AMBUSH™™ System is designed to provide effective "system based" full-surface AND seal fire protection for external floating roof storage tanks. Effective full-surface fire protection may be delivered by an experienced response team deploying significant water and foam resources via largevolume (Big Gun) manned transportable fire monitors, which are staged some distance from a burning tank — offering "over the top" trajectory and safe attack distances. This projection of water/foam solution onto the surface of the tank from a ground position is referred to as a "Type 3 Application". As a seal protection option, traditional fixed foam systems (foam chambers, or foam pourers) are referred to as providing a "Type 2 Application" — delivering a "cascading application" of water/foam solution from unmanned systems affixed to the tank itself. This method of delivery commonly results in lower application volume targeting the seal area. This delivery proves inadequate to extinguish a full-surface fire scenario.

Delivered from outside the tank, consideration must be given to "fallout" of a Type 3 application — the water/foam solution that does not land inside the tank due to wind or general stream erosion from the ground assault. The benefit of a fixed system "Type 2 Application" is a potential increase in foam application density, ie: gallons-per-minute required per square foot of storage tank surface area. Mounted to the rim of the tank, the AMBUSH™ configuration delivers a Type 3 Application toward the center of the tank for full surface protection, while simultaneously delivering lateral Type 2 application streams along the tank wall for seal fire protection. The elevated position of the AMBUSH™ system at the tank rim reduces / eliminates wind erosion and delivers a more forceful seal area application — reducing application times and using less water and foam concentrate than a strict "Type 3 Application".


As a fixed system component, the AMBUSH™ provides a quicker response time and less man power than a portable large volume delivery approach. Also, as a fixed system the AMBUSH™ requires less flow rate due to lower recommended application densities (gpm per ft2 of surface area exposed). Finally, use of the system requires less specialized training and exposes less personnel to a hazardous situation.


The AMBUSH™ System is available in several different sizes. Each size functions similarly. The stream is broken into 4 components. The left/right discharge streams are equal to each other and deliver foam left/right of the unit against the tank wall. The upper stream discharges foam at a slight angle toward the center of the tank. The fourth stream discharges foam back against the tank’s shell and protects the area just below the unit with a small stream.

As the multiple foam streams projecting toward the center of the tank converge, they extinguish the fire in the center of the tank then build back toward the tank’s shell. At the same time, the left/right streams project foam around the circumference of the tank extinguishing any fire near the tank shell. As the tank shell fire is extinguished, this coverage begins to grow toward the center of the tank to meet the foam blanket being established by the upper stream. Soon after, the entire tank will have a full foam blanket.


Model Tank Size Flow Range (GPM)
AMBUSH™ 3305 Up to 160’ 411 - 682
AMBUSH™ 4421 From 161' to 230' 696 - 1154
AMBUSH™ 5541 From 231’ to 310’ 949 - 1573
AMBUSH™ 6661 From 311’ to 360’ 1138 - 1888
AMBUSH™ 6681 From 361’ to 410’ 1328 - 2203
AMBUSH™ 8811 From 411’ to 500’ 1708 - 2832

NFPA recommendations regarding from chamber foam runs require a 40-foot foam run in under 2:00 minutes as a minimum performance measurement.

Williams Fire & Hazard Control testing has shown a typical foam chamber foam run barely meets the requirement, extinguishing a test pan at 40 feet in 1 minute 57 seconds, while the seal area foam application of the AMBUSH™ system will protect 120 feet of seal area extinguishing a test pan at 120 feet in under 2:00 minutes!