Air purifiers are a first line of defense against the dangers of air pollution. That’s because in the case of air pollution, indoor air quality problems are the result ofoutdoorair quality problems. Short-term source reduction of air pollution is rarely an option, and ventilation won’t help either because the outdoors airisthe problem. That leaves remediation as the only practical approach to address air pollution in most situations. And the primary tool for remediation of indoor air pollution is an air purifier.

Usually, discussions about air purifiers, air pollution and air quality focus on particle pollution and ozone pollution. Now a new study from the University of California (UC) Davis Health System focuses on nitrogen oxides, gaseous lung irritants that result from the same fossil fuel burning processes that produces particle pollution. The new study determined that nitrogen oxides are adding significantly to elevated incidences of acute bronchitis and other respiratory illnesses in children who live in polluted areas. The study also found that levels of nitrogen oxide currently considered safe might actually pose a risk for young children. The study results were published this week in the journal Environmental International.

The study was conducted in the Czech Republic, in areas where nitrogen oxides are regularly monitored. The link between elevated nitrogen oxides and acute respiratory illness was strongest in children between the ages of 1 and 2. The researchers determined that a nitrogen oxide exposure of 35 micrograms per cubic meter increased the incidence of acute bronchitis by about 30 percent.

Under normal conditions the level of nitrogen oxides in a home is about half the level outside. In homes with gas stoves, kerosene heaters, etc., the levels indoors can sometimes exceed outdoors levels (in which cases ventilation makes sense). While the effectiveness of high-performance HEPA air purifiers against particle air pollution is clear and proven (IQAir air purifiers can even reduce tiny ultrafine particles by more than 99.5 percent), gases require a filter designed for that purpose. IQAir’s HealthPro Plus and GC MultiGas air purifiers, for example, both contain filter specifically designed to address gases in addition to the systems’ particle filters.

One common form of nitrogen oxides is nitrogendioxide, a gas that is exceptionally damaging to health and is monitored by air quality agencies. In California, the Air Resources Board established ambient outdoor standards that are stricter than federal standards. The California standard is 0.18 parts per million. The heaviest concentrations of nitrogen dioxide in air pollution are in large urban areas such as the Northeast Corridor, Chicago and Los Angeles, according to the American Lung Association. Levels tend to be most elevated near highways.

While air purifiers cannot offer complete protection against nitrogen oxides such as nitrogen dioxide, they can reduce the presence of such dangerous gases. Since the geographic areas with elevated pollution levels of these pollution-related gases are mostly where particle pollution is also a substantial health threat, current and prospective owners of air purifiers in these areas would do well to consider whether their particular air purifier can rid the air of not only particle pollution but can also provide some level of protection against dangerous gases in the polluted air as well.