Impact of the Tepid Water Shower and Eyewash Standards
Recent changes to emergency shower and eyewash standards in ANSI Z358.1-1998 have long-reaching effects that specifying engineers need to take into consideration now for future planning.
OSHA Standard 29 CFR 191.151(c) requires eyewash and shower equipment for emergency use where the eyes or body of an employee may be exposed to injurious materials. OSHA then references the ANSI standard for details. The ANSI standard, of course, establishes minimum performance and use requirements for the following types of equipment: emergency showers, eyewash equipment, eye/face wash equipment, hand-held drench hoses, and combination shower and eyewash or eye/face wash equipment.
Changes to the ANSI standard have a direct impact on the approximately 140,000 people injured each year because of exposure to hazardous materials. ANSI Z358.1 is valued by planners, hygienists and safety specialists as the source on uniform minimum requirements for equipment performance, and information regarding installation, testing, maintenance and training.
The most significant change in the recently revised standard, approved in April 1998, is that it mandates the delivery of tepid water-moderately warm or lukewarm-for 15 minutes at 20 gpm in emergency showers and 0.4 gpm in plumbed emergency eyewash units. Without specific numerical references in the standard, the tepid range is generally considered to be 78 degrees F to 92 degrees F, based somewhat on the normal surface temperature of the human eye. There is no grandfathering provision; a cold shower is simply no longer compliant.
Although the standard is a recommendation and not yet required by law, OSHA generally defers to the most recent standard. Current OSHA standards still reference the 1990 version of ANSI 358Z.1, which did not specify the use of tepid water. Temperature is referenced in the appendix and could range from 60 to 95 degrees. The burning and chilling effects of using water outside this range of temperatures have been well-documented in independent studies. In some cases, water temperature can even accelerate a chemical reaction.
In the 1998-revised standard, ANSI has more specifically defined "tepid."
Why the change? ANSI recommends that if a person comes in contact with any hazardous material, the exposed areas should be flushed for at least 15 minutes. Drench showering with very cold water poses a health hazard to employees and a liability problem to employers. Icy water discourages adequate washdowns, because it is an obvious deterrent to stepping under a shower, much less staying there for 15 minutes. When contaminated clothing is removed for thorough cleaning, the use of cold water contributes to possible shock and hypothermia.
From ANSI's standpoint, the use of tepid water encourages proper use of drench showers in emergency situations and helps prevent bodily heat loss.
Mixing Valves IncludedOlder methods used to supply ambient water to emergency shower and eyewash units required large quantities of stagnant water, which produced bacterial hazards and storage space issues. Newer designs are more cost-efficient and effective, and typically include thermostat-like mixing valves with the use of domestic hot water.
"A lot of owners do not understand the purpose of the mixing valve-that it allows their water heaters to be turned up to an adequate temperature to prevent Legionella from growing in the water heaters, and that the mixing valve mixes cooler water with the hot water to provide a safe water temperature to the rest of the building," notes Sam Reed, director of systems engineering at BSA Design Services.
Engineers need to be aware that it is much more cost-effective to install tepid water now for what will inevitably become an OSHA requirement. It will be prohibitively expensive to add tepid water to projects currently under construction later, after OSHA formally adopts the 1998 standard. In the interim, some regulating agencies are even adopting the new standard on their own; the Texas Education Agency, for example, has mandated tepid water for emergency fixtures in its schools serving students in kindergarten through grade 12.
Design ChallengesFrom a design point of view, tempering water for emergency showers and eyewash applications is challenging. Certain design criteria are unusual and need to be considered when designing a tepid emergency shower or eyewash system. The first is that combination drench and eyewash units are frequently used. The fixture has a high flow rate for the drench and a low flow rate for the eyewash. In order for the valve to have both high and low flow control, it needs to incorporate some unique design features.
A second design consideration is temperature spike, which occurs when large, equal quantities of hot and cold water are mixed instantaneously, creating a spike in the outlet temperature. In domestic water applications, the piping system has time to flatten a temperature spike. In an emergency situation, however, valves are typically installed very close to the fixture. Mixing valves must respond very quickly to flatten a temperature spike.
Another consideration from general valve design is that a majority of domestic water valves are designed to restrict flow in the event of hot or cold water failure. These valves generally meet ASSE 1017. However, when installed on an emergency shower, they can create a dangerous situation. In an emergency, cold water is better than no water; in a domestic water situation, that would be unacceptable.
Therefore, it is crucial to select a valve specifically designed to handle the different events that occur in emergency application. The changing guidelines are prompting some product innovation in the plumbing industry.
Lawler's 911T Tempered Water Mixing Valves are among the "new generation" of single-valve solutions that comply with ANSI Z358.1-1998. In the design stage, we had some very specific criteria to meet. The valve had to provide tepid water at designated flow rates, obviously, but it also had to respond safely to hot and cold water supply failures. If the hot water supply fails, the valve has an integral bypass into cold; if the cold water supply fails, the valve has a tight shut-off of hot water flow.
Lawler's patented dual thermostatic elements eliminate concerns about thermostat failure. This redundant feature provides for a backup system. If one thermostatic element fails, the other still provides tepid water. If any one of the thermostats fail, the valve shuts the hot port and has integral bypass to minimum flow requirement of a full cold dedicated system (20 gpm, 30 psi for 15 minutes). We wanted to eliminate the need for water storage, and it was essential that the unit easily integrate into existing water systems. Customers had to be able to test, flush and repair it within existing plumbing systems. It had to work well for retrofitting.
Other RequirementsIn addition to requiring delivery of tepid water, ANSI Z358.1-1998 recommends the following for all plumbed and self-contained emergency showers, eyewash equipment, eye/face wash equipment, hand-held drench hoses, and combination shower and eyewash or eye/face wash equipment:
- Ten-second travel time. Specific distance references were removed from the 1998 standard; the planner must choose a location based on the estimated time of travel of a person with compromised vision. Equipment shall be in accessible locations that require no more than 10 seconds to reach.
- Clear and level path of travel. Equipment shall be located on the same level as the hazard and the path of travel shall be free of obstructions that may inhibit the immediate use of the equipment.
- Controls. Also called activation devices, pull rods, pull cords, push plates, trays, flags, triangles or treadles, the controls must cause flushing fluid flow within one second. The ANSI standard specifies user visibility and durability. Stay-open valves are specified to ensure continuous flow while freeing up the hands to remove clothing or hold the eyelids open.
- Freeze-protected showers. Where the possibility of freezing conditions exists, equipment shall be protected from freezing or freeze-protected equipment shall be installed.
- Greater sign visibility. Each emergency shower/eyewash/hose location shall be identified with a highly visible sign positioned so the sign shall be visible within the area served by the shower.
- Annual inspections. Equipment shall be inspected annually to assure conformance with ANSI Z358.1 requirements.
- Simultaneous shower/eyewash use. Combination units must be connected to a system capable of supplying adequate flushing fluid to meet the requirements of each component when all components are operated simultaneously. Combination unit components shall be capable of operating simultaneously and shall be positioned so that components may be used simultaneously by the same user.
- Third-party certification. The manufacturer is responsible for third-party verification of performance requirements as specified in the standard.
As part of a potable water system, plumbed emergency shower and eyewash stations are subject to debris, traffic, vibration and fluctuating ambient temperatures, all of which can affect their effectiveness. The revised ANSI standard therefore reinforces the previous recommendation of weekly testing to ensure their correct operation.