Radiation Puts HEPA Filters on the Frontline
April 18, 2011
In one sense, it’s almost comforting to think of radiation as an IAQ problem - a very big one - but whose first line of defense could be a HEPA filter. In another sense, it’s disconcerting to think of its likelihood due to the number of existing nuclear plants. (There are 104 commercial reactors in the United States, according to the U.S. Nuclear Regulatory Commission.)
The earthquake-tsunami events in Japan certainly became much more disturbing, and dangerous, when they set off a chain reaction that resulted in the radioactive releases at the Fukushima Dai-ichi nuclear plant. They alarmed not only the communities nearby, but also those in Hawaii and along the West Coast of the U.S. mainland, and in other countries.
We now know that the immediate threats to those areas are greatly reduced, because of the relatively quick rate of decay, or half-life, of radioactive particles like cesium-137 and iodine-131 and the particles’ dilution in the atmosphere. But it drew attention to the entire nuclear power industry, and led many people to play the “what if” game - “What if a natural disaster led to a nuclear event near me?”
What many people may not know is that relatively common IAQ products, HEPA and ULPA (ultra-low particulate air) filters, are a viable first line of defense against airborne radiation. The important thing is to have such products installed and functioning optimally at the time an event occurs, not after the fact.
HEPAs. REALLY.Jim Carlson, who wrote the ASHRAE Handbook chapter section on radiological events, is with the Omaha Public Power District. He confirmed that “HEPA can filter out particles that may be radioactive.”
The contaminants’ gaseous half-life “is very, very short,” he confirmed. Releases from Japan would decay well before reaching the mainland or even Hawaii. “Anything particle-sized would fall out of the airstream,” he added. “The danger [from the Japan event] is negligible.”
Circul-Aire (a unit of Dectron Internationale), St. Laurent, Quebec, Canada, focuses on cleaning indoor air from industrial and severe contaminants - the tough jobs. Their phones have been ringing in response to the Japan events. “A lot of people are still concerned,” said Nick Agopian, vice president of sales-marketing.
People who already have their air-cleaning systems, he said, “want to know if they are ready to go. There is a lot of interest from residential too,” he added. “They want to know, ‘Is there anything I can put in my house right now?’”
HEPA or ULPA filtration can be a good first line of defense, Agopian said, followed by a carbon-based scrubber. “True HEPA filters may be able to control particles in people’s homes.”
In addition to applying a tested HEPA filter, ventilation effectiveness needs to be considered, he said, to ensure that the particles do not settle out of the airstream. The rate of air changes/hour needs to be high enough to be able to move the air out of the room and into the system, he said. That would be 12-15 changes/hour with a small filter.
“You don’t want to give it a chance to settle,” he said. “How do you get the contaminant from the breathing zone to the filter? Say a space is 20 by 30 feet, and 9 feet high; it needs a minimum 540-cfm airflow to be effective in that room.” This is one reason why room units are worthless, he said. “You’re basically filtering the air for your desk,” or whatever else is in the immediate proximity of a room unit.
The key, Agopian said, is to make sure that the system is already functioning whenever an event takes place, because looking for solutions after the fact is much less effective. He also advised looking at the various potential chemical threats, not just nuclear plants, in any given area. “If you know you live in an area where there is a chemical plant, you should get appropriate filtration.”
CHANGING FILTERSOnce you mention using filtration for airborne radiation, the next logical question is, how do you change the filters? And then, how do you dispose of them?
We checked in with Fred Kobie, owner of Kobie Kooling and Kobie Inspection Services, Fort Myers, Fla. He knows his way through the jungle of personal protective equipment (PPE) for service and maintenance employees.
“With the developments following the Fukushima Daiichi nuclear plant accident, there have been a lot of questions raised about PPE for those industries that are likely to come into contact with radioactive material,” he said. “More specific are the fears of exposure to the isotopes cesium-137 and iodine-131. These isotopes have a relatively short half-life of eight days, but pose a serious risk with certain exposures.
“These isotopes are particles that are able to be filtered, and the HEPA and ULPA filtration of a respirator offers good protection to prevent ingestion,” he said. Appropriate PPEs can include a good personal half-face respirator, along with a PRD (personal radiation detector) tag.
“For long-term exposure [hours], a Tyvek disposable suit will also filter out most alpha particles,” Kobie said. “The primary concern is ingestion, so the eyes, airways, and open wounds are more vulnerable. The National Institute for Occupational Safety and Health also recommends an elastomeric respirator for maximum protection.” This is similar to the PPEs his employees use on HVAC jobs with potential contaminants - in short, nearly all the work that entails opening up an existing HVAC system.
“The concentration of alpha and beta particles in a filter system is the primary concern of a technician in the IAQ and HVAC industries. How do we protect ourselves from the potential of exposure when dealing with the service of filtering systems? The use of personal protective equipment, such as a HEPA filter respirator mask, adds the maximum protection without 100 percent closed air systems.
“The N95 dust mask offers little to no protection against the isotopes,” he added.
PRDs also can be used to measure exposures; the level of personal protection can range from half-face HEPA masks, to full-face, fully enclosed, self-contained breathing apparatus, he said.
“With the levels of radiation measured and the type of radiation we are dealing with, the best preventive tool is the knowledge of the risk and the warning signs of radiation sickness,” Kobie said. “Using common sense and relatively inexpensive HEPA filtration masks reduces the risks. Alpha radiation will not penetrate closed skin,” he said, “and the best (and most convenient) decontamination is soap and water.”
Regarding disposal, “There are huge guidelines,” said Carlson. “We have HEPA filters that are changed and bagged; trained workers take it to a low-level radiation system. You have to be involved in that industry; you don’t want to not know what you’re doing. In good radiation practices, the focus is on containment.”
“When you have an adverse scenario, you have forces that can’t be held back,” Agopian said. “The reactors in Japan were designed for an 8.2-magnitude earthquake.” The quake was 8.9-9.0.
For more information, visit www.circulaire.com and www.kobiekool.com.
Sidebar: Wet Towels?Just how effective were the very first strategies used in Japan - the wet towels around doors and windows? “It’s absolutely effective,” said Agopian. “By sealing a space with water, you’re keeping things from floating in or out,” he said. In loosely constructed Japanese structures, contaminated air may still get in at window frames and around doors, where the wind can push in outdoor air. “The wet towel absorbs those particulates,” he said.
It’s for very, very low concentrations, he added, calling it a Band-Aid until a better solution is possible.
The primary concern in Japan was for the protection of first responders, Agopian said. The company also provided a water purification system. Units in the Caribbean and Haiti were being mobilized to get into Japan. Its five-stage filtration includes a fiber prefilter, HEPA filter, two-stage carbon media, and a fiber afterfilter. “International WaterMakers (IWM) take humidity out of the air,” said Agopian. “It ices up the evaporator coil intentionally,” producing 1 gallon of filtered water for 14 cents.
Sidebar: Relief AidIn support of those affected by the earthquake, the Daikin Group donated 100 million yen in monetary aid, and approximately 200 million yen in material (600 commercial-use air purifiers and 500 far-infrared electric heaters), for a total contribution equivalent of more than 300 million yen.
The company, which is located in an area of Japan distant from and unaffected by the events, has solicited donations from its employees for contribution to the disaster relief efforts.
On March 12, Daikin established an Emergency Response Headquarters headed by Noriyuki Inoue, chairman and CEO. The company said it has been working in support of relief efforts for the disaster areas, with priority placed on “the preservation of life, safety, and tranquility.”
For more information, visit www.daikin.com.
Publication date: 04/18/2011