ASHRAE+62.1-2022+(1) - Page 025

Extracted Content

6.2.1.2.2 Personalized Ventilation Systems. A personalized ventilation system shall be designed in accordance with the following subsections, or the zone air distribution effectiveness ( Ez ) shall be determined in accordance with Normative Appendix C.

Informative Note: A personalized ventilation system is primarily for exposure control and dilution of contaminants in the breathing zone and may provide some spot cooling. Personalized ventilation is used when the occupant spends most of their time in one occupied space. The ventilation outlet is usually incorporated into or mounted on the furniture. It is used in conjunction with another air distribution system that handles the area ventilation requirements and thermal loads in the space.

6.2.1.2.2.1 Personalized Air. The personalized air shall be distributed in the breathing zone and designed such that the velocity is equal to or less than 50 fpm (0.25 m/s) at the head/facial region of the occupant.

6.2.1.2.2.2 Return Air. The return air openings or pathways shall be located more than 9 ft (2.8 m) above the floor.

6.2.1.3 Zone Outdoor Airflow. The zone outdoor airflow ( Voz ) provided to the ventilation zone by the supply air distribution system shall be determined in accordance with Equation 6-2.

Voz = Vbz / Ez (6-2)

6.2.2 Single-Zone Systems. For ventilation systems wherein one or more air handler supplies a mixture of outdoor air and recirculated air to only one ventilation zone, the outdoor air intake flow ( Vot ) shall be determined in accordance with Equation 6-3.

Vot = Voz (6-3)

6.2.3 100% Outdoor Air Systems. For ventilation systems wherein one or more air handler supplies only outdoor air to one or more ventilation zone, the outdoor air intake flow ( Vot ) shall be determined in accordance with Equation 6-4.

Vot =  all zonesVoz (6-4)

6.2.4 Multiple-Zone Recirculating Systems. For ventilation systems wherein one or more air handler supplies a mixture of outdoor air and recirculated air to more than one ventilation zone, the outdoor air intake flow ( Vot ) shall be determined in accordance with Sections 6.2.4.1 through 6.2.4.4.

6.2.4.1 Uncorrected Outdoor Air Intake. The uncorrected outdoor air intake ( Vou ) flow shall be determined in accordance with Equation 6-5.

Vou = D  all zones ( Rp × Pz ) +  all zones ( Ra × Az ) (6-5)

6.2.4.1.1 Occupant Diversity. The occupant diversity ratio ( D ) shall be determined in accordance with Equation 6-6 to account for variations in population within the ventilation zones served by the system.

D = Ps /  all zones Pz (6-6)

where the system population ( Ps ) is the total population in the area served by the system.

Exception to 6.2.4.1.1: Alternative methods to account for occupant diversity shall be permitted, pro vided the resulting Vou value is not less than that determined using Equation 6-5. 6.2.4.1.2 Design System Population. Design system population ( Ps ) shall equal the largest (peak) number of people expected to occupy all ventilation zones served by the ventilation system during use.

Informative Note: Design system population is always equal to or less than the sum of design zone population for all zones in the area served by the system because all zones may not be simultaneously occupied at design population.

6.2.4.1.3 Other Ventilation Requirements. When a zone ventilation rate is obtained from criteria other than this standard, the ventilation rate shall be converted to cubic feet per minute (cfm) or litres per second (L/s) and the value added to Vou for use in system design calculations.

6.2.4.2 System Ventilation Efficiency. The system ventilation efficiency ( Ev ) shall be determined in accordance with Section 6.2.4.3 for the Simplified Procedure or Normative Appendix A for the Alternative Procedure.

Informative Note: These procedures also establish zone minimum primary airflow rates for VAV systems. 6.2.4.3 Simplified Procedure 6.2.4.3.1 System Ventilation Efficiency. System ventilation efficiency ( Ev ) shall be determined in accordance with Equation 6-7 or 6-8.

ANSI/ASHRAE Standard 62.1-2022 23