Potent Greenhouse Gas Eliminated
|Fume hoods are standard equipment in most research labs, providing safe working areas for laboratory workers and researchers, but each one consumes as much energy to operate as three to four average homes.
CREDIT: Rhett Miller, UC San Diego
In an important environmental victory, UC San Diego and the University of California Office of the President have persuaded state regulators to drop a requirement that UC campuses use a potent greenhouse gas in a required laboratory safety test. The change approved by the California Occupational Safety and Health Administration (Cal-OSHA) applies only to the 10 UC campuses in the state, but could eventually be applied across California to reduce energy use and the emission of greenhouse gases.
The state ruling grants UC campuses the ability to permanently stop using sulfur hexafluoride (SF6) gas in the required tests of newly retrofitted energy-efficient laboratory fume hoods. UC San Diego will immediately switch to nitrous oxide gas, a less environmentally hazardous alternative. The ruling does not apply to the California State University system or other colleges, universities, companies and research institutes in California.
Fume hoods are standard equipment in most research labs: they provide safe working areas for laboratory workers and researchers who must handle hazardous solvents and other volatile materials. The fume hoods are continually ventilated through air ducts with powerful fans. The continuous flow of room air into the hoods to roof-top vents requires constant heating or cooling to maintain needed room temperatures.
The push by UC San Diego and the UC Office of the President to seek the variance stems from the university’s concern that SF6 is 22,800 times more potent than carbon dioxide in warming the Earth’s lower atmosphere. Each 20-minute test of a single fume hood using SF6 releases the equivalent of about 10 metric tons of carbon dioxide. The substitute, nitrous oxide, has about 1 percent of the global-warming impact of SF6.
"This change represents a victory for common sense, as well as a significant reduction in UC San Diego's carbon-equivalent footprint,” said Ray Weiss, a distinguished research professor of atmospheric chemistry at Scripps Institution of Oceanography at UC San Diego. “Nitrous oxide is still a significant greenhouse gas, which also plays a role in the depletion of stratospheric ozone, so I hope that we will not rest on our laurels and that we will continue to lead the University of California to even more benign testing procedures."
The colorless, odorless SF6 gas is non-toxic to humans, but Weiss noted that in addition to its strong greenhouse-gas effect it remains in the atmosphere for thousands of years. Nitrous oxide is degraded after about 120 years in the atmosphere.
The state Occupational Safety and Health Standards Board approved the variance application after research by Technical Safety Services Inc. showed that nitrous oxide worked just as well as SF6 and worker safety would not be compromised.
“We confirmed the safety and efficiency of using nitrous oxide as a substitute for a very bad greenhouse gas,” said Larry Wong, program manager of UCOP’s Office of Environment, Health and Safety. “We also are doing the research necessary to change the national consensus standard on this kind of test on hundreds of thousands of fume hoods in the nation.”
The application for the variance was triggered by UC San Diego’s switch to more energy-efficient hoods. As part of the retrofit of hundreds of fume hoods, motion sensors were added that are designed to reduce the flow of room air through the hoods when they are not in use.
“This ruling gives us an opportunity to both reduce our costs and to operate in a more environmentally friendly manner,” said Garry MacPherson, director of Environment, Health and Safety at UC San Diego. “The university will continue to seek additional ways to operate and test our fume hoods in the safest, most cost-effective ways possible.”
A “tracer gas” test is required by Cal-OSHA to ensure that any volatile materials in the hoods are contained when the air flow slows.
The fume-hood retrofits are part of a $73 million energy-efficiency project at UC San Diego involving 25 of its older buildings. The project will reduce total campus energy consumption by at least $6 million a year. The project won’t actually cost UC San Diego any money in the long run because the university could receive an estimated $14 million in incentives from San Diego Gas & Electric. The remaining $59 million will come from low-interest revenue bonds that UC San Diego will repay with cost savings.
“The old-style fume hoods draw in room air 24 hours a day and exhaust it from roof vents and the resulting energy usage is equivalent to 3.5 average homes per hood,” said John Dilliott, manager of energy operations for UC San Diego. “The retrofitted hoods will use about 40 percent less energy, which amounts to a significant savings for the campus.”
Cal-OSHA regulations mirror the testing standards developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). The engineering society’s specifications, adopted in 1995, state: “The tracer gas shall be sulfur hexafluoride” or a similar gas. While nitrous oxide is different in some regards to SF6, the state variance nevertheless allows UC campuses to permanently switch to nitrous oxide.
“It’s ironic that state-mandated safety testing of fume hoods results in a significant release of greenhouse gases in an environmentally conscious state like California,” said Gary C. Matthews, vice chancellor of Resource Management and Planning at UC San Diego. “While the new Cal-OSHA variance is a major environmental victory for UC San Diego, which we call a ‘living laboratory for climate solutions,’ we think our experience in this case will help promote the wider use of more environmentally benign tracer gases in California, the nation and in other countries.”
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