Prevention of Significant Deterioration (PSD)

Another provision of the Clean Air Act with some applicability to wildland burning activities is the prevention of significant deterioration (PSD) provisions.  The goal of PSD is to prevent areas that are currently cleaner than is allowed by the NAAQS from being polluted up to the maximum ceiling established by the NAAQS.

Three air quality classes were established by the Clean Air Act PSD provisions including:

• Class I: allows very little additional pollution (includes wildernesses and national memorial parks over 5,000 acres, National Parks exceeding 6,000 acres, and all international parks that were in existence on August 7, 1977, as well as later expansions to these areas)
• Class II:  allows some incremental increase in pollution 
• Class III:  allows pollution to increase up to the NAAQS

Historically, EPA has regarded smoke from wildland fires as temporary and therefore not subject to issuance of a PSD permit; whether or not wildland fire smoke should be considered when calculating PSD increment consumption or PSD baseline was not defined. EPA recently reaffirmed that States could exclude prescribed fire emissions from increment analyses provided the exclusion does not result in permanent or long-term air quality deterioration (EPA 1998). States are also expected to consider the extent to which a particular type of burning activity is truly temporary, as opposed to an activity that could be expected to occur in a particular area with some regularity over a long period. Oregon is the only State that has chosen to include prescribed fire emissions in PSD increment and baseline calculations.