Have you ever stepped into the shower in the morning in a state of grogginess, only to be instantly awakened by a stream of water that is too hot or too cold? Now imagine seven to eight times the volume of water, at the same temperature, completely immersing your body in an emergency safety shower. In both cases, your body would likely subconsciously respond by jumping out of the uncomfortable water flow.
Why is this exactly? Well, the human body strives to maintain a steady internal temperature within a normal range of 89 to 100 degrees F (32 to 38 degrees C). Actual body temperatures vary from person to person, depending on activity levels and ambient temperature.
When the body encounters a temperature significantly (10 degrees F or more) above its core temperature, it reacts. Blood vessels close to the surface of the body dilate to allow more blood flow in the area. This removes heat from the skin and prevents the core temperature from rising too high. A corresponding reduction in blood flow to the organs occurs to maintain safe blood pressure levels.
The opposite actions occur when the body experiences extreme cold. Immersion in cold water can lead to hypothermia. Water conducts heat away from the body much quicker than air does. Blood vessels near the surface contract to limit the blood flow and prevent the loss of body heat. Internal blood vessels dilate to compensate, causing a higher blood flow through the organs. This puts more strain on the heart as it works harder than usual to keep up.
In both of these cases, the body is working to maintain a safe core temperature. Along with the cardiovascular system changes, the natural human reaction is to withdraw from the temperature extreme to protect the body. But what happens when a person is injured by a chemical splash or caustic burn on the job and the temperature of the water in the emergency safety shower or eye wash is too hot or too cold?
Unfortunately, on top of their injury, they would also face conflicting impulses. Keep in mind that water flow from emergency showers is not like the shower in your home. Most home shower heads deliver 2 to 3 GPM of water flow. Emergency safety showers deliver a minimum of 20 GPM, for 15 minutes. The injured person knows they should remain under the shower for 15-minutes to flush the chemical from their skin but when experiencing a deluge of freezing or scalding water, the body’s natural urge is to exit the shower and protect its core body temperature.
This reaction is why the ANSI/ISEA Z358.1-2014 standard for emergency safety showers and eye wash stations requires tepid water temperatures. In an emergency when life-changing injuries or even death may result, an affected user seeking first aid needs to keep their eyes and body in the stream of water as long as possible to mitigate further injury.
How an Emergency Safety Shower’s Tepid Control System Works
To meet the ANSI standard and keep employees safe, emergency safety showers and eye washes need a method to control water temperature, such as:
- Gravity-fed tank systems are self-contained units that can be used in cold and hot environments, without the need for plumbed potable water. With the capacity for 15-minutes of flushing, the elevated vessels are designed to keep the tank water in the tepid range. They accomplish this by continuously warming water with immersion heaters or cooling water with chillers.
- If you have both hot and cold-water sources, a thermostatic mixing valve is the simplest way to control the temperature. Set at a preferred temperature in the tepid range. It meets this setpoint by mixing hot and cold water together. But, since it is a mechanical device and capable of failing, make sure the valve is designed for emergency showers and eye wash equipment and bypasses to cold water if the valve isn’t functioning properly. The hot water temperatures fall in the 140 to 160 degrees F (60 to 71 degrees C) range, which would severely scald users in case of failure. This way, in case of failure, it will bypass to cold water supply to prevent scalding.
- Tempering solutions such as low-pressure steam is another way to heat a cold-water supply at the point of use. The mixing valve for steam applications has a pressure sensing controller and allows cold water flow even if the heat source is not available. It’s most suitable for use in very cold climates. However, this form of mixing can require a great deal of ongoing maintenance.
- Some tempering water systems use electrical power for heating via a heated vessel using a thermostatic blending valve or an instantaneous water heater. They rely on a high enough water pressure from the facility for the flow of blended water, so it’s vital that the infrastructure can provide adequate power, water pressure and water volume. Electrical systems must also conform to the hazardous area classifications in terms of intrinsic safety.
Other methods of controlling water temperatures include tempered loop systems and mobile tempered water solutions.
Contact Hughes Safety Showers for Tepid Water Solutions
Hughes Safety Showers has more than 50 years of experience across the globe, in many industries, and in a variety of extreme climate conditions. All our equipment meets ANSI Z358.1 requirements. Our experts provide compliance advice and solutions that keep your employees safe. We also offer free site surveys. For more information, contact us today.