Victims are often exposed to hazardous chemicals such as corrosives (acids and bases), oxidizers, and solvents. The object is to both remove the hazardous materials to halt further injury, and to mitigate the effects of the exposure to that point. Since contact with most hazardous materials requires at least 15 minutes of immediate and constant flushing, having the correct volume of water and a minimum water pressure available are critical.
Three choicesThere are three emergency shower system variations to consider: 1) Plumbed-in assets, where there is access to municipal water; 2) Air-charged systems offering a stable, low-mounted water supply that is pressure fed for use, via bottled compressed air; and 3) Gravity-fed systems that have a supply of water suspended over the emergency equipment until needed. Each of the three variations can be configured as a shower, eyewash or combination system.
The best solution is a plumbed-in system in the closest proximity to potential use. That's because plumbed-in equipment tempers the water and can most easily treat multiple victims. Tempering supply water minimizes the possibility of hypothermia, which can occur when a victim is exposed to the temperatures of many areas' tap water for 15 continuous minutes. And since plumbed-in systems have the shortest recovery time, their ability to treat multiple victims is readily apparent.
If the water supply is either unstable or not available at all, your best choice is air-charged shower/eyewash systems. In these products, a sufficient volume of water is held for use at the system, in a pressurized state, and is consistently fed through the emergency equipment at the proper pressure (up to 50 psi), for the entire 15-minute shower cycle.
In comparison, many gravity-fed systems do not hold sufficient volumes of water to properly address the ANSI standard. Basic calculations of volume and pressure indicate that a 1,200-liter holding tank, for example, cannot supply the ANSI required minimum of 20 gpm over a full 15-minute use cycle. Some gravity-fed systems have the ability to refill the holding tank while in operation. But that refill process (at a typical 10 psi) will not keep pace with the outflow. Thus, the level in the tank constantly diminishes throughout the use cycle.
Also, the design of gravity-fed equipment uses the water pressure created by elevating the tank above the system, as well as the physical pressure of the weight of the water in the tank pressing downward. As indicated, the water level drops throughout the use cycle. This leads you to believe that the pressure will also decrease, most likely to below the ANSI required 20 gpm minimum flow rate.
Remember, you need the correct volume of water and a minimum water pressure available to get the most from your emergency shower equipment.