ASHRAE+62.1-2022+(1) - Page 016
Extracted Content
5.13.3.2.2 Recirculation or transfer of Class 2 air to other Class 2 or Class 3 spaces shall be permitted, provided that the other spaces are used for the same or similar purpose or task and involve the same or similar pollutant sources as the Class 2 space.
5.13.3.2.3 Transfer of Class 2 air to toilet rooms shall be permitted. 5.13.3.2.4 Recirculation or transfer of Class 2 air to Class 4 spaces shall be permitted. 5.13.3.2.5 Class 2 air shall not be recirculated or transferred to Class 1 spaces. Exception to 5.13.3.2.5: When using any energy recovery device, recirculation from leakage, carry over, or transfer from the exhaust side of the energy recovery device is permitted but shall not be counted as outdoor air. Exhaust air transfer ratio of Class 2 air shall not exceed 10% of the outdoor air intake flow at the design static pressure differential as defined in AHRI 1060.
5.13.3.3 Class 3 Air 5.13.3.3.1 Recirculation of Class 3 air within the space of origin shall be permitted. 5.13.3.3.2 Class 3 air shall not be recirculated or transferred to any other space. Exception to 5.13.3.3.2: When using any energy recovery device, recirculation from leakage, carry over, or transfer from the exhaust side of the energy recovery device is permitted but shall not be counted as outdoor air. Exhaust air transfer ratio of Class 3 air shall not exceed 5% of the outdoor air intake flow at the design static pressure differential as defined in AHRI 1060.
5.13.3.4 Class 4 Air. Class 4 air shall not be recirculated or transferred to any space or recirculated within the space of origin.
5.13.4 Documentation. Design documentation shall indicate the justification for classification of air from any occupancy category, airstream, or location not listed in Table 6-1, 6-2, or 6-3.
5.14 Exhaust Duct Location 5.14.1 Exhaust ducts that convey Class 4 air shall be negatively pressurized relative to ducts, plenums, or occupiable spaces through which the ducts pass.
5.14.2 Exhaust ducts under positive pressure that convey Class 2 or Class 3 air shall not extend through ducts, plenums, or occupiable spaces other than the space from which the exhaust air is drawn.
Exception to 5.14.2: Exhaust ducts conveying Class 2 air and exhaust ducts conveying air from residen tial kitchen hoods that are sealed in accordance with SMACNA Seal Class A.
5.15 Combustion Air. Fuel-burning appliances, both vented and unvented, shall be provided with air for combustion and removal of combustion products in accordance with manufacturer’s instructions. Products of combustion from vented appliances shall be vented directly outdoors.
5.16 Local Capture of Contaminants. The discharge from noncombustion equipment that captures the contaminants generated by the equipment shall be ducted directly to the outdoors. Exception to 5.16: Equipment specifically designed for discharge indoors in accordance with the manufac turer’s recommendations.
5.17 Building Exfiltration. Ventilation systems for a building equipped with or served by mechanical cooling equipment shall be designed such that the total building outdoor air intake equals or exceeds the total building exhaust under all load and dynamic reset conditions.
Exceptions to 5.17:
- Where an imbalance is required by process considerations and approved by the AHJ, such as in certain industrial facilities.
- When outdoor air dry-bulb temperature is below the indoor space dew-point design temperature.
Informative Note: Although individual zones within a building may be neutral or negative with respect to outdoors or to other zones, net positive mechanical intake airflow for the building as a whole reduces infiltration of untreated outdoor air.
5.18 Ventilation System Controls. Mechanical ventilation systems shall include controls in accordance with the following subsections.
5.18.1 All systems shall be provided with manual or automatic controls to maintain not less than the outdoor air intake flow ( Vot ) required by Section 6 under all load conditions or dynamic reset conditions.
5.18.2 Systems with fans supplying variable primary air ( Vps ) shall be provided with any combination of control equipment, methods, or devices to maintain no less than the outdoor air intake flow ( Vot ) required for compliance with Section 5.18.1.
14 ANSI/ASHRAE Standard 62.1-2022