Eyewash Safety: Keeping Water in the Comfort Zone

Make sure your equipment delivers ANSI-required tepid water to eye and eye/face washes to encourage a full 15- minute flush.

• By Ryan Pfund
• Oct 01, 2013

When bathing, we all have a personal "comfort zone" for water temperature. If the water’s too hot or too cold, chances are we’ll cut the shower or bath short.

The same concept applies to eye and face wash fixtures, in which water temperature plays a significant role in ensuring someone will drench long enough to remove all hazardous chemicals from affected areas. Due to the potential risks to workers -- and the responsibility of owners to protect them -- it is important that all new and existing systems have a tepid flow of water to encourage a full rinse.

ANSI Z358.1 requires that tepid water be delivered to emergency fixtures, which encourages an injured party to complete the full 15-minute flush during an emergency. ANSI suggests an incoming water temperature between 60and 100 degrees F.

Despite the requirement, maintaining tepid water is often overlooked, most likely due to time and cost. Some assume that cold water will be sufficient for eyewash or drench shower fixtures, but the flushing fluid needs to be delivered at a comfortable temperature that is not harmful to the user. If the water is below 60 degrees F, prolonged exposure can affect the body's ability to maintain its body temperature, increasing the risk of hypothermia. Most commonly, cold water will simply cause the user to leave the drench or rinse before the 15-minute guideline, risking bodily damage. Conversely, if the fluid delivered to the affected user is over 100 degrees F, the chemical reaction could be accelerated, or if hot enough, it could cause skin scalding.

Water supply to the unit also must be sufficient to support a full 15-minute flow of flushing fluid. For both drench showers and eyewashes, a minimum water pressure of 30 pounds per square inch (PSI) should be supplied to the unit. It must also satisfy the ANSI minimum flow rate, which is at least 20 gallons per minute (GPM) for drench showers, 0.4 GPM for eyewashes, and 3.0 GPM for eye and face washes. Actual flow rates vary based on the product, so it's important to verify flow rates with the equipment manufacturer.

For some, in a pinch, supplemental products can provide a source of quick, immediate relief, but they cannot replace the more critical need for a full 15-minute rinse with tepid water. It's essential for every potential hazard to be supported by a plumbed or portable device that has access to an adequate water supply at an appropriate pressure and temperature.

Delivering Tepid Water
Emergency thermostatic mixing valves (TMVs), as well as specially designed on-demand water heaters, are effective solutions for delivering tepid water consistently and reliably to emergency fixtures. Both technologies help ensure that the user will stay in the water rinse for the full 15 minutes.

TMVs. With TMVs, the hot and cold water is brought into the valve, where it is mixed together and then routed over an internal thermal element called a thermostat. The thermostat continuously maintains the temperature of the mixed water flowing through the TMV. If the temperature differs from the valve's set temperature, the thermostat will react and move a mechanism that modulates one or both of the inlet ports until the valve returns to the set temperature, thus ensuring that each emergency fixture is provided with tepid water.

Keep in mind not all TMVs are designed for tepid water. It's important to know that there is a difference between standard thermostatic valves and thermostatic mixing valves designed for emergency fixtures. Standard thermostatic mixing valves are designed to shut off the flow of water if there is a loss to either the hot or cold water supply. This is acceptable for typical domestic situations where a supply of only hot or only cold water would shock someone taking a shower.

However, an emergency application is different in that it’s better for someone to shower in cold water than no water at all. For this reason, emergency valves are designed with a cold-water bypass. Should the thermostat fail or the valve lose its hot water source for any reason, the cold water would still be allowed to flow through the valve to the emergency fixture. If the cold supply is lost, the valve will shut off and prevent the hot water from flowing through the valve to the emergency fixture. This protects the user from the potential dangers of a hot flushing fluid being supplied to the eyewash or shower.

Electric tankless water heaters. There are new, tankless heating systems that are especially efficient and precise in immediately supplying tepid water for use in eyewash and drench shower systems because they contain additional safeguards to prevent scalding of an injured worker. Newer models draw energy only when needed, hold outlet temperature to within plus or minus 1 degree F, and have a low pressure drop (as low as 8 pounds per square inch). Systems with this capacity will minimize potential post-installation complications due to a sudden pressure drop, resulting in minimal pressure at the fixture.

Built with redundant safety and anti-scald features to meet ANSI tepid water requirements, newer heaters quickly can reach the required tepid water temperature and provide injured employees with a consistent flow of tepid water for 15 minutes. Some heaters also offer overshoot purge protection that will automatically open to purge excess hot water when necessary.

From an operational efficiency standpoint, because newer tankless water heaters draw energy only when needed, they can provide significant energy cost savings. In addition, installation of these units is simplified because only one electrical connection and a cold water line are needed.

Keep in mind that tankless water heaters are often sized improperly. While most look only at the average ground water temperature, these products need to be configured based on the lowest ground water temperature. This will ensure the unit heats the water to the proper temperature during the coldest time of the year.

Getting Help for Your Installation
Consulting with a third-party safety consultant and/or an emergency equipment product manufacturer can help determine what type of heating mechanism is best for specific work environments. When dealing with the health and safety of employees, knowing that the appropriate emergency fixtures are installed correctly and prepared with tepid water will promote proper usage and peace of mind for all.

This article originally appeared in the October 2013 issue of Occupational Health & Safety.