Indoor Pollutant Levels from the Use of Unvented Natural Gas Fireplaces in Boulder, Colorado

Abstract

High CO and NO2 concentrations have been documented in homes with unvented combustion appliances, such as natural gas fireplaces. In addition, polycyclic aromatic hydrocarbons (PAH) are emitted from incomplete natural gas combustion. The acute health risks of CO and NO2 exposure have been well established for the general population and for certain high-risk groups, including infants, the elderly, and people with heart disease or asthma. Health effects from PAH exposure are less well known, but may include increased risk of cancer. We monitored CO emissions during the operation of unvented natural gas fireplaces in two residences in Boulder, CO, at various times between 1997 and 2000. During 1999, we expanded our tests to include measurements of NO2 and PAH. Results show significant pollutant accumulation indoors when the fireplaces were used for extended periods of time. In one case, CO concentrations greater than 100 ppm accumulated in under 2 hr of operation; a person at rest exposed for 10 hr to this environment would get a mild case of CO poisoning with an estimated 10% carboxyhemoglobin level. Appreciable NO2 concentrations were also detected, with a 4-hr time average reaching 0.36 ppm. Similar time-average total PAH concentrations reached 35 ng/m3. The results of this study provide preliminary insights to potential indoor air quality problems in homes operating unvented natural gas fireplaces in Boulder.

Particle size distributions and concentrations of airborne endotoxin using novel collection methods in homes during the winter and summer seasons

“…¼ 0.18 h )1 ). These data span the mean infiltration rate of 43 southern California homes of 0.63 ± 0.33 h )1 (Lee et al, 1999), and agree with the air exchange rates of 0.2-0.6 h )1 measured in three other residences in Boulder, Colorado (Dutton et al, 2001).…”

Results of the C alifornia H ealthy H omes I ndoor A ir Q uality S tudy of 2011–2013: impact of natural gas appliances on air pollutant concentrations

“…A recent simulation study estimated that among southern California homes that cook at least once per week with natural gas and do not regularly use a venting range hood, more than half have 1-h NO 2 concentrations exceeding 100 ppb and roughly 5% have short-term CO concentrations that exceed the concentration thresholds of acute ambient standards on a weekly basis in winter (Logue et al, 2014). Homes that use unvented gas heaters and fireplaces can have particularly high concentrations of combustion pollutants, often exceeding AAQS thresholds (Dutton et al, 2001;Francisco et al, 2010;Ryan et al, 1989). In homes with gas appliances, smaller home size and the presence of floor and wall furnaces have been associated with higher combustion pollutant levels (Wilson et al, 1986).…”

Measured concentrations of combustion gases from the use of unvented gas fireplaces

“…There have been few field measurements of the in situ concentrations of combustion products in homes using unvented fireplaces. One study looked at carbon monoxide (CO) and nitrogen dioxide (NO 2 ) concentrations in two homes in Boulder, Colorado (Dutton et al., 2001). In these homes, the unvented fireplaces were operated continuously for extended periods of time.…”