Air Cleaners for Removal of Odorous Compounds Associated with the Aliso Canyon Natural Gas Leak
Filter Replacement for Homes Receiving Portable and In-duct Air Cleaners
Residents receiving air cleaners and filters from SoCalGas to help reduce the odorous compounds from the gas leak are encouraged to follow the steps outlined below:
- Use the air cleaner(s) provided as needed.
- Review the owner’s manuals carefully regarding instructions for maintenance and filter replacement, and follow all instructions. However, if you have been operating the air cleaners continuously or for much of each day, you may need to replace the filters and/or activated charcoal or carbon beds more frequently than recommended in the owner’s manual.
- Check the filters and air cleaners at least once a month for odors, excess dust accumulation, or other problems that might indicate a need for replacement.
- There is no way to know exactly when a filter needs replacement. Increased noise and reduced airflow are other possible indicators that a filter may need to be replaced.
In general, thinner filters and those with less activated charcoal (carbon) will need to be changed more often. This would include those filters with 1 inch or less depth and/or less than 3 lbs. of activated charcoal. Air cleaners with deep activated charcoal beds (2 inches or more) and/or large quantities of activated charcoal (about 5 or more lbs.) such as those found in the IQAir and Austin Air Systems portable air cleaners should last longer.
If you have Franklin activated charcoal filters that were installed when the AirScrubber Plus models were installed in the central air system, they will need to be replaced often (every 2 to 3 months) during times when the air is polluted, because they are relatively thin filters. For homeowners concerned about gaseous chemicals in their home, a Franklin filter with activated charcoal or another comparable model would be appropriate. Because the leak has been plugged, owners can consider returning to a “particle filter only” model. ARB recommends that all homeowners use at least a medium efficiency particle filter for the central heating and air system, and where possible a high efficiency particle filter (see pages 2-4 in the document linked below). These are the higher quality (non-see through) filters available at most local hardware stores and home stores and online. Be sure to purchase the correct size filter for the filter slot; a filter that does not exactly fit the filter slot will allow air to flow around it, resulting in less air being filtered.
For further information regarding air filters, including information on medium and high efficiency filters, see Air Cleaning Devices for the Home: Frequently Asked Questions.
Some Basics about Air Filtration
Many commonly used residential air cleaners will not effectively remove the odorous mercaptans and other sulfur-containing components of the Aliso Canyon natural gas leak from the air. However, several companies sell specialized models that should effectively reduce indoor levels of those and other chemicals emitted during gas leaks.
- Air filters with activated charcoal will remove benzene (and other volatile organic compounds), and those with additives such as potassium permanganate will remove most mercaptans (the ‘smell’ of natural gas) and other odorous gases related to gas leaks, such as hydrogen sulfide.
- Note: None of the filters will capture methane which does not pose a health risk itself in this situation.
- Thinner filters need to be replaced more frequently than thicker filters.
- If you smell any odors coming from the filter, it is likely time to change that filter.
Portable Air Cleaners
The most effective air cleaners for homes are portable models with deep beds (large quantities) of activated charcoal combined with potassium permanganate or similar oxidizing substances that are able to remove most of the odorous (i.e., mercaptans/sulfur) compounds. Such models can be relatively expensive and specialized.
Air cleaners with activated charcoal alone can remove benzene and many volatile organic compounds (VOCs), including some amounts of certain sulfur compounds. But these air cleaners are not as effective at removing sulfur compounds as those that contain potassium permanganate or similar additives.
A portable air cleaner must be sized properly for the volume of air to be cleaned. Check the square footage or volume of air the air cleaner can treat, and compare it to the square footage of the home or volume of space to be treated to determine how many air cleaners will be needed. Typically a two-story home will require at least one unit on each floor.
Portable units generally use less energy than an in-duct device installed in the central heating and air system. When two or more portable units are needed, however, there may be little difference in the total energy needed to clean the air compared to a central system.
Another advantage of portable units is that they can be moved to areas where residents spend most of their time, such as the main living area during the day and a bedroom at night, to assure rapid cleaning of the air nearest the occupants.
SoCalGas Air Cleaners
The California Air Resources Board (CARB) has reviewed some air cleaners offered by Southern California Gas (SoCalGas) to assess whether those air cleaners are likely to help reduce the levels of the chemicals of concern in homes affected by the gas leak. Based on available information from manufacturers, the models listed below should be effective in reducing indoor concentrations of the odorous chemicals. Also, based on the manufacturer’s specifications for power consumption, the estimated monthly energy cost for each unit is provided in the table below. This is based on a 24 hour per day, full month usage profile at the current tier-one energy rate ($0.15/kWh). Your actual costs may vary depending on your specific rate structure and usage.
Table of Portable Air Cleaners
Estimated Energy Use (kW) - Low Setting
Estimated Energy Use (kW) - High Setting
Estimated Monthly Energy Cost - Low Settingi
Estimated Monthly Energy Cost - High Settingi
IQAir GC Multi-Gas
12 lbs. of activated carbon and alumina impregnated with potassium permanganate
IQAir HealthPro Plus
5 lbs. of activated carbon and alumina impregnated with potassium permanganate
Austin Air HealthMate Plus (HM450)
15 lbs. of granular carbon/zeolite impregnated with potassium iodide
Austin Air HealthMate Plus Jr. (HM250)
7 lbs. of granular carbon/zeolite impregnated with potassium iodide
Blueair AB 500 series (503, 550E, 555EB)
12 lbs. max. (3 filters each with 4 lbs. of activated carbon formulated with magnesium dioxide and copper oxide)
Blueair AB 600 series (603, 650E)
12 lbs. max. (3 filters each with 4 lbs. of activated carbon, formulated with magnesium dioxide and copper oxide
Blueair Pro XLii
1 lbs. max. (3 filters each with 1/3 lbs. of activated carbon, formulated with magnesium dioxide and copper oxide)
18 lbs. of enhanced activated carbon
AeraMaxPro AM IV
8.8 lbs. (2 filters each with 4.4 lbs.) blend of activated alumina impregnated with activated carbon (50%) and virgin activated carbon (50%)
AeraMaxPro AM III
4.4 lbs. blend of activated alumina impregnated with activated carbon (50%) and virgin activated carbon (50%)
Alen BreatheSmart (with Copper Oxide/Carbon filter media)ii
About 1.5 pounds of activated carbon and 1.5 pounds of activated carbon impregnated with copper oxide
Oransi Erik (OV190) with activated carbon (Pre-Erik) filterii
3.5 lbs. of activated carbon impregnated with potassium permanganate
i Estimate of the monthly electricity costs to operate the portable air cleaner model in a residence for the lowest and highest fan settings, assuming an electricity rate of $0.15/kWh (based on general tier 1 utility information). This cost assumes continuous air cleaner operation of 24 hours/day. Keep in mind that these figures are only estimates, and that the actual cost may vary depending on other factors (i.e., your electricity provider and the rate tier being charged by your provider).
ii This device may require more frequent filter changes due to the lower amount of activated carbon it contains.
iii This device will remove some odorants but may not be as effective as those with the added oxidizers impregnated into the activated carbon.
The charcoal beds (and most particle filters) will need to be replaced periodically, following manufacturer’s instructions. They may need more frequent replacement than recommended if they are used in a heavily polluted area. Additional information regarding replacement frequency is provided below.
Methane is not removed by any of these models to any substantial degree. Methane is an odorless, colorless gas and does not have noticeable health effects at the levels observed from this leak (about 2 to 50 parts per billion).
In-Duct Air Cleaning Devices
Some in-duct devices utilizing an ultraviolet (UV) bulb may also be effective at removing some of the offensive chemicals. However, certain UV bulbs emit ozone, which is not recommended in areas occupied by people due to its harmful health impacts. UV bulbs that emit light at the 254 nanometer (nm) wavelength and block the shorter wavelengths should not produce ozone.
In-duct air cleaning devices typically use more energy than portables because in-duct devices can only remove pollutants when the central air system is on, and central systems utilize large, powerful motors to move the air throughout the ducts and the house.
SoCalGas has installed AirScrubber Plus in-duct units (which use ultraviolet bulbs that do not produce ozone) along with Franklin activated charcoal filters in many homes. Together these units should remove benzene and many other VOCs, but are expected to remove only some of the mercaptans and sulfur compounds. AirScrubber Plus in-duct units require continuous operation of the home’s central ventilation system to achieve maximum air cleaning. Compared to running the central system intermittently when the heater trips in, the central ventilation systems can use nearly 500% more energy, corresponding to an increase in monthly electricity usage of about 422 kWh. Assuming an electricity rate of $0.15/kWh, the estimated monthly energy cost associated with AirScrubber Plus in-duct unit is $63.30. Also, it should be noted that these units need to be installed or removed by trained technicians.
Other technologies may also be effective at removing the odorous chemicals. However, in a recent California Air Resources Board-funded study conducted by scientists at Lawrence Berkeley National Laboratory, some air cleaners using other technologies (i.e., photocatalytic oxidation [PCO]) were found to emit a larger quantity of chemicals than they removed, and some of those chemicals are potentially harmful to health.
Other types of air cleaners, including some with activated charcoal, can emit chemicals and/or produce odors with use. Thus, air cleaners should be selected carefully (see below) and always maintained as recommended.
State regulation requires all air cleaners sold or distributed in California to be certified as not exceeding 50 parts per billion of ozone when tested using a specified test method. CARB offers a list of certified air cleaner models on its web page. Note that this certification only covers ozone emissions and electrical safety; it does not include performance testing for removal of particles or chemicals from the airstream. Other brands may be added to this list in the future.
For questions regarding California’s air cleaner certification or models, contact firstname.lastname@example.org.