Issue link: https://hi.iaq.net/i/630729
HVAC Systems and Indoor Air Quality 137 used because source strength is usually not known. Whichever procedure is utilized in the design, the standard states that the design criteria and assumptions shall be docu- mented and made available to those responsible for the operation and mainte- nance of the system. Important features of ASHRAE 62- 1989 include: ■ a definition of acceptable air quality ■ a discussion of ventilation effectiveness ■ the recommendation of the use of source control through isolation and local exhaust of contaminants ■ recommendations for the use of heat recovery ventilation ■ a guideline for allowable carbon dioxide levels ■ appendices listing suggested possible guidelines for common indoor pollutants Standard 55-1981, "Thermal Environmental Conditions for Human Occupancy" ASHRAE 55-1981 covers several environ- mental parameters including: temperature, radiation, humidity, and air movement. The standard specifies thermal environ- mental conditions for the comfort of healthy people in normal indoor environ- ments for winter and summer conditions. It also attempts to introduce limits on the temperature variations within a space. In addition to specifications for temperature and humidity, guidelines are given for air movement, temperature cycling, tempera- ture drift, vertical temperature difference, radiant asymmetry, and floor temperatures. Adjustment factors are described for various activity levels of the occupants, and different clothing levels. Important features of this standard include: ■ a definition of acceptable thermal comfort Water Chillers Water chillers are frequently found in large building air conditioning systems because of the superior performance they offer. A water chiller must be maintained in proper working condition to perform its function of removing the heat from the building. Chilled water supply temperatures should operate in the range of 45°F or colder in order to provide proper moisture removal during humid weather. Piping should be insulated to prevent condensation. Other than thermal comfort, IAQ concerns associated with water chillers involve potential release of the working fluids from the chiller system. The rupture disk (safety release) of the system should be piped to the outdoors, and refrigerant leaks should be located and repaired. Waste oils and spent refrigerant should be disposed of properly. ASHRAE STANDARDS AND GUIDELINES Standard 62-1989, "Ventilation for Acceptable Air Quality" ASHRAE 62-1989 is intended to assist professionals in the proper design of ventilation systems for buildings. The standard presents two procedures for ventilation design, a "Ventilation Rate" procedure and an "Air Quality" procedure. With the Ventilation Rate procedure, acceptable air quality is achieved by specifying a given quantity and quality of outdoor air based upon occupant density and space usage. Examples of the tables listing the prescriptive amounts of outdoor air for the Ventilation Rate procedure are presented at the end of this section. The Air Quality procedure is a perfor- mance specification that allows acceptable air quality to be achieved within a space by controlling for known and specifiable contaminants. This procedure is seldom