Welding shops for educational facilities, whether they are part of a high school technology program or a technical college, are significantly different from industrial welding operations. In the educational setting, the purpose of the programs is solely to teach the student to become proficient in various types of welding and maybe specialize in advanced welding techniques after the basics have been mastered. Students are typically in a welding class for a few hours a day or maybe even just a few hours per week. In industry, a welder is employed by a company where they are often required to weld daily for extended periods of time. Recognizing that there is a difference in the levels of exposure to welding fumes, the question that must be answered by the design professional is, should the ventilation requirements for the educational environment be relaxed as compared to the ventilation requirements for the industrial environment, and, if so, how much and what do governmental regulations have to say about this issue? Instinctively one might answer that the regulations should be applied similarly to both, but that is clearly not reflected in current design practices.
Welding fumes aren’t good to breath, and all regulatory agencies agree that welding fumes should be directed away from the welder’s breathing zone when local exhaust ventilation (LEV) is being used. While all fumes are bad, some fumes are recognized as more hazardous than others. One such fume is hexavalent chromium, which is produced when welding stainless steel and other materials containing chromium. During the welding process, the chromium is heated, oxidation occurs, and it is converted into hexavalent chromium. Hexavalent chromium is also designated by the following: chromium (VI), hexchromium, Cr (VI), Chromium + 6, and Cr + 6. It is classified as a carcinogen. There are other elements present in some welding fumes, such as manganese, that are also very harmful, but hexavalent chromium has gotten most of the attention over the past 25 years as the result of the extensive use of stainless steel in various industries including the nuclear industry, water treatment industry, and many others.
In 1994, several parties filed lawsuits with the government claiming that the Occupational Safety and Health Administration (OSHA) had failed to act in a timely manner to implement a stronger standard for exposure to hexavalent chromium. The claim was that OSHA was aware that the permissible exposure levels (PEL) for hexavalent chromium for workers in several industries was much higher than it should be and that workers were getting very sick and dying from exposure to it. The PEL in 1994 was 52ug/m3 and OSHA was being asked to reduce it to 0.25 ug/m3. It wasn’t until almost 2007 when the new PEL went into effect. Initially, OSHA indicated that the PEL would be changed to 1 ug/m3. When the final language was released, the PEL was established at 5 ug/m3 - 20 times higher than what some industrial groups requested it be set at in 1994. It is interesting to note that OSHA has, in recent years, suggested that the recommended exposure level (REL) be set at .2ug/m3. Unfortunately, it has been estimated that more than 500,000 persons in this country have been exposed to hexavalent chromium.
Present OSHA regulations require that employers must assess their workers exposure to hexavalent chromium for a time weighted 8-hour average (8-hour TWA) for each work area and for the welding activities in that space. If the level is 50 percent or greater than the PEL, the space must be monitored every six months. If the employer can demonstrate that fumes for the space are less than 10 percent of the PEL, less than .5 ug/m3, monitoring does not have to be performed. When exposure levels are above the PEL, the space must be monitored every three months, and employees are required to be equipped with respirators.
So, how bad is hexavalent chromium? In 2000, the movie, “Erin Brockovich,” was released. Hexavalent chromium was the subject of that movie in which ground water in Hinkley, California, was contaminated. As a result of the lawsuit filed in 1996, Pacific Gas and Electric (PGE) agreed to pay a settlement of $333 million. There are reports that indicate PGE has spent more than $700 million trying to clean up the hexavalent chromium, and, according to PGE, it is estimated that it will be several more decades before the cleanup will be complete.
Another example of concern people have about hexavalent chromium is expressed in arguments over the amount of acceptable chromium levels in municipal drinking water. Chromium exists in multiple forms in drinking water including chromium 3 and hexavalent chromium (chromium 6). Chromium 3 is not harmful, and, therefore, the concern is only with the hexavalent chromium. The problem for the public is that most municipal water analysis reports only show the total chromium and not the level of hexavalent chromium component. The current level of chromium allowed by the Environmental Protection Agency (EPA) in drinking water is 100 ppb. Several states have argued that the current EPA level is too high and that the drinking water reports should state the amount of hexavalent chromium in the drinking water. California recently became the first state to establish a maximum level of hexavalent chromium in drinking water at 10 ppb. The California Department of Public Health has taken this a step further and proposed a goal level of .02 ppb – 500 times less than their stated maximum level. The EPA has not lowered the levels below 100 ppb but has indicated that this is something they are reviewing.
So, how does this relate to welding ventilation systems and particularly the systems in educational facilities? In educational facilities there are three ventilation design approaches commonly used by design professionals. The first is a ducted ventilation system, either with individual fans or a central ventilation system, in which all the welding fumes are exhausted directly to the building exterior. It seems plausible that the exposure level of hexavalent chromium would never exceed the 10 percent PEL threshold with direct fume exhaust (depending upon style of welding booth, backdraft, etc.), and, therefore, no monitoring would be required. The second design is the central ventilation system where fumes are exhausted, filtered, and recirculated back into the building. The third system is the ductless welding booth in which the ventilation fan and filtration is integral with the welding booth, and the filtered fumes are vented directly back into the space. The reasons to provide ductless welding booths may include such considerations as: less expensive filters than with a central ventilation system; when there is a problem with the central ventilation system, many welding stations are impacted at one time; a centralized system requires a relatively large amount of space outside the building for the equipment; and unless the centralized ventilation system is oversized in the initial installation, when additional welding stations are added in the future, the centralized system cannot accommodate the additional airflow requirements. As energy costs continue to rise, the use of filtered, recirculated air is becoming more and more the basis of design for not only industrial applications but education applications as well.
The questions for the engineer and owner designing a recirculating welding ventilation system are, first, is hexavalent chromium produced and in what quantities and, second, what other design considerations are important? The answer, in part, should be that the design should provide the level of filtration appropriate for the quantity of hexavalent chromium being produced (including possible future levels) and the air quality which you are trying to achieve for the space and its occupants. For an industrial environment, the level of filtration where recirculating systems are utilized may be easier to determine than in an educational setting since the type and intensity of welding in the industrial environment may be easier to quantify. In addition, the workers’ environment in an industrial setting is much more regulated than in an educational environment. The greater amount of welding in an industrial environment almost always dictates a high level of filtration be provided as compared to the educational environment. The challenge for the educational environmental design is how to determine the appropriate level of filtration when utilizing a recirculating system. That is often left up to the facility director, welding instructor, and/or the design professional. The level of filtration that ultimately gets provided is often determined by what filtration is available from the ductless welding booth selected for the project and not necessarily by what level of filtration is actually needed.
The centralized ventilation system allows the designer to select any level of filtration that is desired up to and including HEPA filtration. The higher the level of filtration, the higher the cost of the filters, the system, the installation, and the operation. If an owner chooses not to utilize a centralized ventilation system and selects a ductless welding booth system, the choice of filters from each of the various ductless welding booth manufacturers may not be the same as with a central system. The options from the ductless welding booth manufacturers vary from panel filters with MERV ratings of 13 to cartridge filters with MERV ratings of 15 or 16. The MERV 13 filters are less than 75 percent efficient for particles in the .3-1.0 micron size range while the MERV 16 filters are greater than 95 percent efficient for the same size particles.
So what do OSHA regulations say about recirculation of fumes containing hexavalent chromium? The OSHA Technical Manual (Section III: Chapter 3: Ventilation Investigation) states that “Recirculation should not be used if a carcinogen is present.” When OSHA was asked how ventilation systems exhausting hexavalent chromium, a carcinogen, can be recirculated as is frequently done, OSHA explains that recirculation is not generally recommended but where used “recirculation should incorporate air cleaners, a by-pass or auxiliary exhaust system, regular maintenance and inspection, and devices to monitor system performance.” We then asked OSHA how self-contained, ductless welding booths comply with OSHA’s recommendations for recirculating welding fumes containing hexavalent chromium. They responded, “These systems may claim to have the ability to maintain safe working levels of hexavalent chromium while welding. These systems may be better suited for welding fumes that do not contain CR (VI). If this type system is used, monitoring would need to be performed to determine the employees’ exposure and determine if respiratory protection may also be required.” We asked about what monitoring devices they were referring to, but we have yet to receive a response to that question. OSHA made it clear to us that they were responding to occupational environments and could not respond to educational environments.
Back to the original question, should government regulations for hexavalent chromium for the industrial environment be relaxed for the educational environment? With regards to filtration, that decision appears to be solely left up to the owner and/or design professional. OSHA Technical Manual states “Protection of employees must be the primary design consideration.” We assume this applies equally to employees in the industrial environment and to students and instructors in the educational environment.
Publication date: 6/5/2017