ASHRAE+62.1-2022+(1) - Page 042
Extracted Content
(This is a normative appendix and is part of the standard.)
NORMATIVE APPENDIX B SEPARATION OF EXHAUST OUTLETS AND OUTDOOR AIR INTAKES
B1. GENERAL
This appendix presents an alternative procedure for determining separation distance between outdoor air intakes and exhaust air and vent outlets. This analytical method can be used instead of Table 5-1.
Exhaust air and vent outlets, as defined in Table 5-1, shall be located no closer to outdoor air intakes, or to operable windows, skylights, and doors, both those on the subject property and those on adjacent properties, than the minimum separation distance ( L ) specified in this section. The distance ( L ) is defined as the shortest “stretched string” distance measured from the closest point of the outlet opening to the closest point of the outdoor air intake opening, or to the operable window, skylight, or door opening, along a trajectory as if a string were stretched between them.
B1.1 Application. Laboratory fume hood exhaust air outlets shall be in compliance with NFPA 45 and ANSI/AIHA Z9.5. Nonlaboratory exhaust outlets and outdoor air intakes or other openings shall be separated in accordance with the following.
B1.2 Outdoor Air Intakes. The minimum separation distance between exhaust air/vent outlets, as defined in Table 5-1, and outdoor air intakes to mechanical ventilation systems, or to operable windows, skylights, and doors that are required as part of natural ventilation systems, shall be equal to distance ( L ) determined in accordance with Section B2. Exception to B1.2: Separation distances do not apply when exhaust and outdoor air intake systems are con trolled such that they cannot operate simultaneously.
B1.3 Other Building Openings. The minimum separation distance between building exhaust air/vent outlets, as defined in Table 5-1, and operable openings to occupiable spaces shall be half of the distance ( L ) determined in accordance with Section B2. The minimum separation distance between either Class 3, Class 4, cooling tower, or combustion appliance/equipment exhaust air/vent outlets and operable openings to occupiable spaces shall be equal to the distance ( L ) determined in accordance with Section B2.
B1.4 Additional Limitations for Noxious or Dangerous Air. The minimum separation distance between exhausts located less than 65 ft (20 m) vertically below outdoor air intakes or operable windows and doors shall be equal to a horizontal separation only as determined in accordance with Section B2; no credit may be taken for any vertical separation.
B1.5 Equipment Wells. Exhaust air outlets that terminate in an equipment well that also encloses an outdoor air intake shall meet the separation requirements of this section and, in addition, shall either
a. terminate at or above the highest enclosing wall and discharge air upward at a velocity exceeding 1000
fpm (5 m/s) or b. terminate 3 ft (1 m) above the highest enclosing wall (with no minimum velocity).
Exception to B1.5: Exhaust air designated as Class 1 or Class 2.
B1.6 Property Lines. The minimum separation distance between exhaust air/vent outlets and property lines shall be half of the distance ( L ) determined in accordance with Section B2. Exception to B1.6: For Class 3, Class 4, or combustion appliance/equipment exhaust air, where the prop erty line abuts a street or other public way, no minimum separation is required if exhaust termination is at least 10 ft (3 m) above grade.
B2. DETERMINING DISTANCE L
The minimum separation distance ( L ) shall be determined using one of the following three approaches.
B2.1 Simple Method. A value of L in Table B-1 shall be used.
B2.2 Velocity Method. The value of L shall be determined using Equation B-1 (I-P) or B-2 (SI).
L = 0.09 × Q × ( DF – U /400) [ft] (B-1)
L = 0.04 × Q × ( DF – U /2) [m] (B-2)
where
Q = exhaust airflow rate, cfm (L/s). For gravity vents, such as plumbing vents, use an exhaust rate of 150 cfm (75 L/s). For flue vents from fuel-burning appliances, assume a value of 250 cfm per
40 ANSI/ASHRAE Standard 62.1-2022