Requirements for Indoor Environment

Requirements for indoor environment quality must be discussed and decided before the air conditioning design is performed. Criteria for acceptable indoor air quality and thermal comfort must be set. 

Health hazard due to exposure to contaminants by inhalation is the most important issue. International or national health and building regulations or codes and recommendations are used as basis for the discussion of what requirements should be used for design. In regulations, worker exposure limits for airbctrne gases are normally expressed as 

Time-weighted average concentration, TWA, based on a 40-hour work week. 

Short-term exposure limit, STEL, which can be exceeded for periods of up to 15 minutes, and 

Threshold limit value, TLV, a concentration level not to be exceeded any time. 

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