ASHRAE Journal - February 2012 - 82

IAQ APPLICATIONS

Ozone and Air Filters
O
By Charles Seyffer, Member ASHRAE

zone can be hazardous to humans even at low levels. Exposure to ozone is linked to premature death, asthma, bronchitis,

heart attack, and other cardiopulmonary problems. Long-term exposure to ozone has been shown to increase the risk of death from respiratory illness.

A study1 of 450,000 people living in U.S. cities showed a signiﬁcant correlation between ozone levels and respiratory illness over the 18-year follow-up period. The study revealed that people living in cities with high ozone levels such as Houston and Los Angeles had a more than 30% increased risk of dying from lung disease. In indoor spaces, ozone, as well as the reaction products of ozone interacting with chemicals found indoors. can cause health concerns. ASHRAE’s Environmental Health Committee (EHC) issued an Emerging Issue Brief on Ozone and Indoor Chemistry2 in January 2011 that reports on research showing that “safe O3 levels would be lower than 10 ppb.” The EHC document describes several actions that can be taken to reduce health impacts of ozone and associated byproducts in indoor spaces. These actions include: removing ozone at outdoor air intakes; minimizing ozone emissions from equipment used indoors; reducing concentrations of terpenes and carbonyls (aldehydes) using source reduction and gas phase removal equipment; and using high-efﬁciency particulate ﬁlters (e.g., MERV3 13 or greater) to remove secondary organic aerosols (SOA) and ultraﬁne particles (UFP) that are created as by-products of ozone reactions.
82 ASHRAE Journal

Existing Strategies for Improved IAQ
Engineers designing new buildings, and retroﬁtting air-conditioning systems in older buildings, must consider outdoor ozone as a pollutant that may have to be removed. Since 1989, ASHRAE has referenced ozone as a contaminant of concern in Standard 62.1, Ventilation for Acceptable Indoor Air Quality. The standard references the National Ambient Air Quality Standards (NAAQS)4 as published by the U.S. Environmental Protection Agency (EPA). The NAAQS includes level details on six pollutants harmful to public health and the environment; particulate matter, nitrogen oxides, carbon monoxide, sulfur dioxide, lead and ozone. For buildings with air change rates of more than 1.5 air changes per hour, ASHRAE Standard 62.1-2010 requires air ﬁlters for ozone removal when the most recent three-year average annual fourth-highest daily maximum eight-hour average ozone concentration exceeds 0.107 ppm (2.09 mg/m3). The EHC Emerging Issue Brief provides information that suggests even this level is far above levels of potential concern. Unfortunately, more than 100 million people in the United States live in areas where ozone may be elevated and the outdoor levels must be considered in
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the design phase, according to the current values published in the NAAQS. Although ozone may be detected by some individuals at levels as low as 10 ppm (chlorine-like odor), its harmful effects exist at much lower levels. ASHRAE/USGBC/IES Standard 189.1-2009, Standard for the Design of High-Performance Green Buildings, speciﬁes that: when the building is located in an area that is designated “nonattainment” with a national ambient air quality standards for ozone as determined by the authority having jurisdiction (in the U.S., by the U.S. EPA) air cleaners having a removal efﬁciency of no less than the one speciﬁed in ASHRAE Standard 62.1, Section 6.2.1.2, shall be provided to clean outdoor air prior to its introduction to occupied spaces. Standard 189.1 also strengthens the requirements to investigate and address outdoor air quality that are contained in Standard 62.1 and mandates remedial actions for the beneﬁt of building occupants. Ozone may also be produced internally by any item that has an electric ﬁeld. In today’s world of desktop computers, printers, copiers, electric motors, etc., we seem to be creating our own ozone chemical soup.

Role of Air Filtration
Historically, engineers have done an exemplary job of addressing particulate matter with the application of air ﬁlters to reduce human exposure in commercial buildings. Today’s air ﬁlters address bacteria, nuisance dusts and other particles that may enter the lungs and cause damage. Still, many systems use ﬁlters with such a low efﬁciency that although they keep coils clean, they do not address the critical submicron particulate related to human health.
February 2012

ASHRAE Journal - February 2012

Table of Contents for the Digital Edition of ASHRAE Journal - February 2012