Class of Loss & Category of Water

Class 1: Slow Rate of Evaporation

Water losses that affect only part of a room with low-permeance/porosity materials (e.g. plywood, particle board, structural wood, VCT, concrete). Little or no wet carpet and/or cushion is present (or damage confined to a small area, or wet for a short period). Minimum moisture is absorbed by materials, which release that moisture slowly.

Class 2: Fast Rate of Evaporation

Water losses that affect the entire room of carpet and cushion. Water has wicked up walls less than 24 inches. There is moisture remaining in structural materials (e.g. plywood, particle board, structural wood, VCT, concrete).

Class 3: Fastest Rate of Evaporation

Water may have come from overhead. Ceilings, walls, insulation, carpet, cushion, and subfloor in virtually the entire area are saturated.

Class 4: Specialty Drying Situations

These losses involve wet materials with very low permeance/porosity (e.g. hardwoods, subfloors, plaster, brick, concrete, stone, crawlspaces). Typically, these are deep pockets of saturation, which normally require very low specific humidity.

Category 1: Clean Water

Originates from a source that does not pose substantial harm to humans.  Examples include broken water supply lines, tub or sink overflows without contaminants, melting ice or snow, falling rainwater, broken toilet tanks/bowls without contaminants, etc.

Category 2: Gray Water

Contains a significant level of contamination and has the potential to cause discomfort or sickness if consumed by or exposed to humans.  Examples include discharge from dishwashing or washing machines, overflows from toilet bowls with some urine (no feces), sump pump failures, seepage due to hydrostatic pressure, broken aquariums, punctured water beds, etc.

Category 3: Black Water

Contains pathogenic agents and is grossly unsanitary.  Examples include sewage, toilet backflows from beyond the trap, and all flooding from seawater, surface waters, rivers, streams, etc.