Ceiling Value

Exposure to manganese dusts, fume, and compounds should not exceed the ceiling value of 5 mg/ms for even short periods because of the element s toxicity level. 

Ceiling value concentration which should not be exceeded not appropriate to use a time-weighted average. 

Ceiling value and skin absorption special measures to prevent significant cutaneous absorption may be required. 

These are ceiling values that must not be exceeded when calculating 8 hr TWA. They should be read in conjunction with biological limits for lead. 

The TLVs for airborne contaminants are based on the premise that although all chemical substances are toxic at some concentration for some period of time, a concentration exists for all substances from which no toxicity may be expected no matter how often the exposure is repeated. A similar premise holds for substances producing irritation, discomfort and nuisance. In using these limits, items such as excursion factors, ceiling values, "skin" notations, mixtures of substances, and inert material should be considered. These factors are discussed below. 

Ceiling Value (CV) The airborne concentration of a potentially toxic substance which should never be exceeded in the breathing zone. 

Ceiling Value—A concentration of a substance that should not be exceeded, even instantaneously. 

Standards for individual substances are usually set to reflect ceiling values, a threshold concentration value never to be exceeded even momentarily, and also time-weighted average values,... 

EPA has established that hydrogen sulfide is a regulated toxic substance and is a hazardous substance as defined under the Federal Water Pollution Control Act. OSH A has established an acceptable ceiling concentration of 20 parts per million (ppm) for hydrogen sulfide in the workplace, with a maximum level of 50 ppm allowed for 10 minutes maximum duration if no other measurable exposure occurs. NIOSH has set a maximum Recommended Exposure Limit (REL) ceiling value (10 minutes) of 10 ppm. A complete listing of federal and state regulations and recommendations are found in Chapter 7. 

Ceiling Exposure limit that specifies the concentration of vapor, dust, or aerosol that should not be exceeded at any time during the workday. In some instances, a time limit for exposure to the ceiling value is established and is indicated in parentheses. A [Skin] notation indicates that percutaneous absorption of the material is a potential hazard and may contribute to the overall exposure. 

Threshold Limit Value (TLV) 0.003 mg/m3 (This is a ceiling value)... 

OSHA sets the levels of chloroform allowed in workplace air in the United States. A permissible occupational exposure limit is 50 ppm or 240 mg/m (ceiling value) in air during an 8-hour workday, 40-hour workweek. 

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