Skip Navigation

Related Topics

Haze - Assessment and Treatment Alternatives

CTU = Conservation Treatment Unit
NCPS = National Conservation Practice Standard
VOCs = Volatile Organic Compounds
NOx = Nitrous Oxides
SO2 = Sulfur Dioxide
NH3 = ammonia
O3 = Ozone

Haze - Traditionally, haze is an atmospheric phenomenon where dust, smoke and other dry particles obscure the clarity of the sky and hence affect visibility. These pollutants include fine particulate matter (PM2.5), and compounds which contribute to PM2.5 formation such as NOx, SO2, certain VOCs, and NH3. Sources for the fine particles that create haze include soil tillage, transportation, manufacturing, and forest fires. The Regional Haze Rule, instituted in 1999 by the EPA, calls for state and federal agencies to work together to improve visibility in 156 National Parks, wilderness areas and designated portions of Indian Reservations. Such areas are known as Class 1 airsheds (see Figure 2). The Clean Air Act defines mandatory Class I Federal airsheds as certain national parks (over 6,000 acres), wilderness areas (over 5,000 acres), national memorial parks (over 5,000 acres), and international parks that were in existence as of August 1977.

Is the CTU near a designated Class I airshed? (Near means <50 km (~31 miles)

Yes or No. This question addresses concerns with regional haze (smoke/visibility) and NOx, O3, VOC, and NH3 factors in formation of haze.

If yes, consider practices/management techniques that reduce or eliminate the potential for smoke and haze precursor generation such as:

  • Emission reduction techniques
  • Use of non-burning alternatives (i.e., chipping, debris removal, and refuse disposal or burial under Forest Slash Treatment  (NCPS Number 384)
  • Crop Residue Management (NCPS Numbers 329, 344, 345 and 346)
  • Smoke management plan (NCPS Number 338)
  • No-till or Minimum Tillage (NCPS Numbers 329, 344, 345 and 346).

Figure 2. Map of mandatory and designated Class 1 Airsheds in Montana









Figure 2. Map of mandatory and designated Class 1 Airsheds in Montana (including but not shown, the Fort Peck and Assiniboine, Confederated Salish and Kootenai, and Northern Cheyenne Reservations). Numbers 1 through 10 within blue borders delineate state designated airsheds in Montana.

Continue on to Greenhouse Gases (GHGs) - Assessment and Treatment Alternatives