by Tom Jones and Ryan Pfund, Bradley Product Managers

In 1998, changes made to the ANSI/ISEA Z358.1 standard for emergency eye wash and shower equipment have had an impact on every worker who comes in contact with emergency fixtures. While the standard is a recommendation and not a law, the Occupational Safety and Health Administration generally will defer to the most recent standard for compliance inspections. Thus, every job-specifying engineer, construction site foreman, employer, and safety director must make sure to understand the standards in order to ensure compliance.

Perhaps the most significant change that occurred with this requirement is that flushing fluids must be delivered tepid. Here's why.

Safety Issues in Water Temperature

In the 1990 version of the ANSI/ISEA Z358.1 standard, water temperature was referenced in the appendix section only, which is not considered part of the standard but is for informational purposes. Water temperature could range from 60 to 95 degrees F.

ANSI did not provide a grandfather clause on the tepid water requirement. Existing emergency fixtures should be brought up to the new standard and new installations should include tepid water in the job specifications.

In the 1998 version of the ANSI standard, each section identifies the need for the delivered water to be tepid. ANSI/ISEA Z358.1-1998 defines tepid as "Moderately warm, lukewarm." ANSI/ISEA Z358.1 also requires a 15-minute flush with minimum performance standards of 20 gallons per minute (GPM) for emergency showers, .4 GPM for eye wash equipment, and 3 GPM for eye/face wash equipment and hand-held drench hoses. Combination shower and eye wash or eye/face wash equipment must meet the minimum performance standards for each part if operated independently, and it also must be capable of supplying adequate flushing fluid should both components be operated at the same time.

The issue that arises is that well water temperatures in North America range from 40 to 60 degrees F, while surface water temperatures can range from 32 to 85 degrees F. While these cold temperatures provide an initial cooling effect to the skin, exposure for the ANSI-required 15 minutes has the potential to cause shock or hypothermia. The end result is that water this cold can be a health hazard to the worker and a liability issue for the employer. The secondary effect of water too cold is that the worker will not stay under the shower for the full 15 minutes, preventing the hazardous material from being washed off the skin. Again, this is a health hazard to the worker and a liability issue for the employer.

Should the delivered flushing fluid arrive to the worker above 100 degrees F, the chemical reaction could be accelerated or, if hot enough, could cause skin scalding. Once more, this is a potential health hazard for the worker and a potential liability issue for the employer. Because chemical reactions can be accelerated in warmer water, the objective is to find the coolest possible temperature the worker will drench under for the full 15 minutes. ANSI includes a provision to consult with a medical adviser for the optimal water temperature based on the application.

ANSI did not provide a grandfather clause on the tepid water requirement. Therefore, all existing emergency fixtures should be brought up to the new standard and all new installations should include tepid water in the job specifications. With plumbed emergency fixtures, that optimal tepid water temperature can be achieved by using a Thermostatic Mixing Valve.

A Solution: Thermostatic Mixing Valves

The proper thermostatic mixing valve can provide a consistent, reliable temperature to the emergency fixture and ensure the person using the fixture will not be subjected to an uncomfortable drenching or washing temperature.

Thermostatic mixing valves work by blending hot and cold water together to reach a desired outlet temperature. The hot and cold water is brought into the valve, mixed together, and made to flow over a thermal element--the thermostat. The thermostat will continually respond to changes in the inlet water temperatures. Should this temperature differ from the set temperature of the valve, 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. This is how the thermostatic valve ensures each emergency fixture has tepid water if it is needed.

An important requirement of a thermostatic mixing valve is to protect the user from a sudden thermal shock. Most thermostatic mixing valves are designed to shut off the flow of water should there be a loss to either the hot or cold water supply. This is fine for typical domestic situations; however, an emergency application is different. It is unlikely a worker exposed to a hazardous material can withstand scalding temperatures for any amount of time, yet it also has been determined that it is better for that worker to rinse in cold water than to not rinse at all. For this reason, emergency valves are designed with a cold water bypass. Should the thermostat fail or if the valve were to lose hot water, the cold water would still be allowed to flow through the valve to the emergency fixture to at least provide the user with water with which to drench. If the cold supply is lost, the valve will shut off, preventing the hot water from flowing through the valve and reaching the emergency fixture.

Emergency valves have a cold water bypass. Should the thermostat fail or if the valve were to lose hot water, cold water still flows through the valve.

Sizing the emergency valve for the specific application is also important. You must ensure that the valve will be able to handle the water demand from the emergency fixture(s). This can easily be seen with combination units that have both a drench shower and eye wash or an eye/face wash. The drench shower demands a high volume of water (ANSI minimum is 20 GPM at 30 pounds per square inch), and the eye/face wash demands a low volume of water (ANSI minimum is 3 GPM at 30 psi). Therefore, it is important to look at the flow rate of the valve you are selecting.

In this example, you would need a valve that is capable of supplying tepid water at a rate as low as 3 GPM or as high as the combined flow rate of the drench shower and the eye/face wash (minimum of 23 GPM, but may be more). Small emergency fixtures such as eye wash units require .4 GPM at 30 psi, meaning a much smaller thermostatic valve will be required.

Most manufacturers offer different size valves to meet the flow requirements of the various emergency fixtures. They also clearly publish the flow rates of each valve under normal operation or cold water bypass operation.

There are a few other important features to look for when selecting a thermostatic valve for an emergency application. Inlet strainer-checkstops are important to prevent cross flow of hot and cold water and to keep dirt and debris from entering the valve. An adjustable set point temperature is important to provide the proper temperature to rinse certain chemicals. An accurate temperature control to within 3 degrees F will help to maintain a reliable outlet temperature. A universal mounting capability will allow the valve to function in any position. Finally, a thermometer will provide an accurate reading of the outlet temperature for the valve.

Conclusion

The 1998 revision to the ANSI/ISEA Z58.1 standard is a positive step for the worker and the employer. It accomplishes the objective of ANSI by encouraging the proper use of an emergency fixture for the required amount of time, while limiting the health risk of the user.

A worker must stay under an emergency shower, or flush his eyes, for the full 15 minutes to get as much of the hazardous material off his body as possible. By using a thermostatic mixing valve designed for emergency fixtures to provide tepid water, worker acceptance and compliance increases, while health concerns and liability issues decrease.

To ensure compliance, look for a properly sized thermostatic mixing valve that has the anti-scald feature, a cold water bypass, an easily adjustable temperature, and an exterior thermometer to ensure proper temperatures. Finally, because ANSI/ISEA Z358.1-1998 offered no grandfather provision, all existing fixtures, and all new installations, must be brought up to the tepid water standard.

 

Tom Jones is the Emergency Fixture Product Manager and Ryan Pfund is the Thermostatic Mixing Valve Product Manager at Bradley Corporation of Menomonee Falls, Wis. Bradley is a manufacturer of emergency fixtures and thermostatic mixing valves and has been in the plumbing fixture business for more than 80 years. For more information on tepid water standards, visit www.bradleycorp.com