Aeronautical Information Manual (AIM), page 542
7110.65R AIM AIM CHG 2 3/15/07 5/26/16 12/10/15 As with mountain wave turbulence or clear air The best available information on this phenomenon turbulence, an invisible plume may be encountered must come from pilots via the PIREP reporting unexpectedly. Cooling towers, power plant stacks, procedures. All pilots encountering hazardous exhaust fans, and other similar structures are depicted plume conditions are urgently requested to report in FIG 7-5-2. time, location, and intensity (light, moderate, severe, Pilots are encouraged to exercise caution when flying or extreme) of the element to the FAA facility with in the vicinity of exhaust plumes. Pilots are also which they are maintaining radio contact. If time and encouraged to reference the Chart Supplement U.S. conditions permit, elements should be reported where amplifying notes may caution pilots and according to the standards for other PIREPs and identify the location of structure(s) emitting exhaust position reports (AIM Paragraph 7-1-22, PIREPS plumes. Relating to Turbulence).FIG 7-5-2 Plumes 7-5-14 Potential Flight Hazards
Page 542 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures