Concerns about odors are well-founded. Unpleasant odors are often an indication that dangerous pollutants are in the air.

Even if the odors don't indicate danger, they can make people ill or at least cause people to curtail activities. How about that picnic to celebrate a 50th wedding anniversary being canceled?

Chemical plants, refineries, power plants and other industrial facilities that hold air pollution permits are subject to state rules regarding emission events. Often referred to as upsets, emission events include air pollution released during malfunctions (accidents), maintenance activities, unit startups and unit shutdowns.

Regulation of emissions from plant flares in Texas is based on flare efficiency studies conducted by the US Environmental Protection Agency (EPA) in the early 1980’s, which concluded that flare combustion efficiencies of 98 or 99 percent are achieved when critical operating variables are controlled appropriately. However, recent studies suggest that, even when well-controlled, flares may operate with efficiencies appreciably lower than 98 percent due to crosswinds and other factors. Lower than assumed flare combustion efficiencies, particularly during emission events, could account for a significant portion of previously unrecognized emissions from refineries and chemical plants and help to explain Houston’s high ozone levels.

This paper discusses the state of the art in understanding flare emissions and examines the specific shortcomings of the current Texas flare regulations, including new regulations on highly reactive volatile organic compounds (HRVOCs). In addition, it considers steps that could mitigate flare emissions, and finally provides a list of recommendations for industry and regulators. Recommendations include expanding research on factors affecting flare combustion efficiency; improving monitoring and reporting of flare operating parameters, such as steam assist and flare gas mass ratios; minimizing the volume of waste gases routed to elevated, unenclosed flares; and encouraging the use of flare gas recovery systems or wind-protected ground flares and thermal oxidizers.