When air pressure inside a building is lower than in the ground, radon, water vapor and other gases can be sucked in from the soil. Chimneys and exhaust fans reduce indoor air pressure. Radon levels tend to be higher during cold weather in leaky homes because warm air leaking up and out through the attic causes indoor air pressure to become lower than the pressure of gasses in the soil.
The pressure-driven flow of radon is through any holes, cracks and pores in concrete. The inflow of soil gas typically ranges from less than 1% to over 20% of the total "fresh air" infiltration into homes. If you reduce either the pathways or the pressure difference, then less radon, water vapor, and other gasses from the soil will enter your home.
Radon is measured in picoCuries
A picoCurie is 0.000,000,000,001
(one-trillionth) of a Curie, an international measurement unit of radioactivity.
One picoCurie per liter (pCi/L) means that in one liter of air there will be 2.2 radioactive
disintegrations each minute. For example, at 4 pCi/L there will be approximately
12,672 radioactive disintegrations in one liter of air, during a 24-hour period.
About one-third of the radon we inhale remains in the body.
 | Map of radon zones in the USA |
Jeff Kramer and C.F. Fox
Understanding the design, operation and maintenance of a building's Heating, Ventilating and Air Conditioning (HVAC) system and how it influences indoor air quality can be beneficial in determining the management strategy for a radon problem. Quite often the problem can be solved without the need for extensive and sometimes costly radon mitigation systems.
The U.S. Environmental Protection Agency (EPA) and other major national and international scientific organizations have concluded that radon is a human carcinogen and can be a serious environmental health problem. Early concern about indoor radon focused primarily on the hazard posed in the home. More recently, the EPA has conducted extensive research on the presence and measurement of radon in buildings. Initial reports from those studies prompted the EPA Administrator to recommend that buildings nationwide be tested for the presence of radon and to reduce elevated levels to below an established "action level".
The EPA recommends action to reduce the level of radon when indoor levels are 4 pCi/I or higher. Testing is the only way to determine whether or not the radon concentration in a building room is below the action level. Measuring levels of radon gas in buildings is a relatively easy and inexpensive process compared to many other important building maintenance activities. Even if elevated levels of radon are found to be present there may be simple, cost-effective, alternative techniques to expensive, installed mitigation systems. One of the first things to check when investigating elevated radon levels is the operation of the HVAC system.
The HVAC systems in buildings can directly influence radon entry due to air pressure differences between the radon laden soil and the building interior. Depending on its type and operation, a building's HVAC system may produce positive or negative pressure conditions within the building. A slightly positive pressure within the building can prevent radon from entering a building while negative pressure can pull radon into the building. The latter was found to be the case in two buildings when the Springfield City Building District had all of its buildings and administration buildings tested.
Fortunately, there were no extremely high radon levels found in any of the classrooms in the district. There were slightly elevated levels found in an administration building and one building's boiler room. The radon concentrations found throughout the administration building ranged from 6 to 16 pCi/L, while the level in the building boiler room was 28 pCi/L. Because the EPA does not recommend taking remedial action based on initial screening tests alone, these same areas were retested one month later to be averaged with the first results. The results of the second screening tests were nearly identical to the initial results.
As the administration building was investigated, the first symptom was the inward draft when outside doors were opened. This indicated that the building was indeed under negative pressure. The construction of the building is of slab-on-grade design (no basement or crawl spaces). An inspection of the floor in 1995 confirmed that there was air infiltration around the baseboards. A new HVAC system had been installed in 1994. The uniformity of the radon measurements suggested that the air turnover rate in the building might be quite low, which was confirmed during the investigation.
An inspection of the HVAC system produced several findings. The air inlet dampers on the rooftop units were closed, providing virtually no makeup air. The only air being exhausted from the building was that which was lost from leaks in the building shell. In winter the "chimney effect" causes this air to escape near the roof line. If the air turnover rate is very low, the air contaminants will build up. Also, as is common for many office buildings, the HVAC system was set back or turned off during evenings and weekends to reduce heating and/or cooling costs. This can also contribute to the build up of radon levels during setback periods. The combination of these factors led us to believe that this building suffered from a lack of ventilation and make up air.
With the help of the district's HVAC specialist, adjustments were made to the computerized HVAC system. The rooftop unit dampers were reset to provide about 50% makeup air, increasing the air turnover rate. The supply air dampers were set to 20% open to increase the circulation of air in the rooms. The set back time when the HVAC system was shut down was reduced to keep the system active longer. In addition, the openings around the baseboards were sealed.
With these corrections made, the building was retested in the same locations. All results of the retests were 2.0 pCi/L or lower, well below the EPA 'action level' of 4 pCi/L. The adjustments made to the HVAC system combined with the baseboard sealing were successful in lowering the radon concentrations.
The investigation of the building boiler room presented one noticeable problem immediately. Combustion air is required for the boilers which creates a negative pressure draw of air into the boiler room. One of the two combustion air dampers which supplies air from outside the building had been improperly installed. The louvers were closed when the boilers were operating. This increased the negative pressure in the boiler room, which would "pull" radon gas through any cracks or crevices in the foundation.
The obvious solution was to correct the reversed louver. When this was done the two combustion air dampers still did not fully supply combustion air to the two boilers without pulling soil gasses in through the foundation. It was decided to install a third damper to increase the air supply to the boilers. This sufficiently reduced the draw of air from below the foundation. A retest of the boiler room showed that the radon level had dropped dramatically from 28 pCi/L to 0.9 pCi/L.
When considering the indoor air quality of buildings like buildings, proper ventilation is a significant part of an overall approach to its improvement. Because buildings vary in their design, construction and operation, it is not possible to recommend standard corrective actions that apply to all buildings. Understanding how the HVAC system influences indoor air conditions is helpful in properly managing a radon problem.
Costs for radon reduction will also be building specific and will depend in part on several factors:
If modifications to an HVAC system are to be feasible long-term mitigation approaches in a given building, then proper operation and maintenance of the system is critical. Performance during various seasonal changes and any additional maintenance and energy costs associated with the changes in operation of the HVAC system must also be carefully considered.
NOTE: Radon mitigation can also help to reduce air conditioning costs and prevent mold problems in basements. Gallons of water from the soil, in the form of vapor, enter a typical home each day. Removal of water vapor by use of air conditioners and dehumidifiers uses significant amounts of electricity. Water vapor, radon, and other gasses in the soil can be blocked from entry into buildings by making sure that the air pressure in the building is slightly higher than the pressure of gasses in the soil.
Jeff Kramer is a licensed Radon
Mitigation Specialist for Brumbaugh-Herrick, Inc. in Toledo, Ohio.
Fred Fox is
Director of Business Services for the Springfield City Buildings.
The EPA says that up to 4 picoCuries of radon per liter of air is "safe", but they also admit that this is up to four times the natural background level, and that 4 picoCuries is the equivalent of getting 200 to 300 chest x-rays per year or smoking 1/2 a pack of cigarettes per day. The EPA says 1% to 5% of the people exposed to 4 picoCuries 75% of the time for 70 years will develop lung cancer.
Radon mitigation can also decrease the entry of moisture and other soil gases into a building, reducing the potential for mold, mildew, methane, pesticide gases and other air quality problems.
Every year, Radon claims about 21,000 people in the United States due to lung cancer. The colorless, odorless gas seeps into homes through the basement. Health and Human Services Environmental Health Programs Manager Todd Falter says Nebraska is a high risk area for radon gas. He says one of every two homes tested in the state comes back with higher than acceptable levels. Radon is a naturally occurring gas that comes from the breakdown of uranium and metals in the soil in the region. Exposure to radon gas is the second leading cause of lung cancer in the United States. Radon testing kits are available at hardware stores. The Nebraska Health and Human Services System is offering vouchers for discounted radon testing kits. Call 1-800-334-9491 for more information. See also: Map of Nebraska radon zones
WHO: Radon Second Leading Cause of Lung Cancer |
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| Geneva June 21,2005 |
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The World Health Organization (WHO) says lung cancer can be cut by minimizing the risks of radon, a natural radioactive gas. The organization is launching a program to reduce the rate of lung cancer around the world.
Radon is a natural radioactive gas that emanates from the ground into the air. It is present everywhere in the world. Its concentration depends on the uranium content of the soil.
The World Health Organization says after smoking, exposure to radon is the second leading cause of lung cancer. And, it adds, smokers exposed to radon have a 25 times greater chance of getting lung cancer than non-smokers.
The head of WHO's Radiation and Environmental Health Unit, Mike Repacholi, says radon exposure causes between six and 15 percent of all lung cancer cases. He says tens of thousands of deaths from this disease annually can be attributed to radon.
Although people all over the world are exposed to this substance, Dr. Repacholi says those living in cold climates are most at risk. He says the greatest exposure to radon for most people is found in the home.
"It is not a big problem in Africa because of the high temperatures and good room ventilation,” said Dr. Repacholi. “The best mitigation measure for radon is to keep your windows open so you have air circulating all the time. Because the amount of radon that is in the outdoor air is diffused to such an extent that it does not become a risk factor. It is only when the radon is accumulated in the home that does not have good ventilation."
Dr. Repacholi says radon exposure in the home is a big problem in the United States, in Europe and Japan. He says it poses potentially big risks in China and northern parts of Afghanistan and Pakistan.
But, he says he is very worried about the situation that exists in countries of the former Soviet Union, including the central Asian republics. He says people there are unaware of the enormity of the problem they face. He says countries in this region have high concentrations of uranium in the soil.
"And with energy prices there, they are going to find out about sealing the windows and making sure that the cold air does not get in. And, so there is going to be, what I think, is quite a large problem there. That compounded with a massive increase in smoking that is going on there could produce quite a large excess numbers of lung cancer," he noted.
Dr. Repacholi says the radon threat to human health can be mitigated with relatively simple measures.
He says building codes should be enacted to minimize the amount of radon allowed to seep into a house. For example, he says a major entry point for radon is through the soil in the basement. He says this can be reduced by increasing under-floor ventilation and sealing cracks and gaps in the floor.
The entry of radon into homes can be substantially reduced by simply keeping indoor air pressure slightly higher than the pressure of gasses in the soil.
