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Ventilation and Air Quality

2 tools in the Building Systems area.

Ventilation Rate

Minimum outdoor airflow of a space by the ventilation rate procedure of ASHRAE Standard 62.1: the breathing-zone rate is the people component R_p times the occupants plus the area component R_a times the floor area, with R_p and R_a from the standard's table for the occupancy category; dividing by the zone air-distribution effectiveness of the supply arrangement gives the outdoor air the system must deliver to the zone. The tool lists the category rates, reports the breathing-zone and zone outdoor airflows, the rate per person and per unit area, and the outdoor-air fraction of a given supply airflow.

Industrial Ventilation and Exhaust Hoods

Local exhaust system design from the hood to the stack: the exhaust flow of each hood from the published capture-velocity relations (plain and flanged openings, slots, canopies, booths and downdraft grilles), the hood entry loss and hood static pressure, branch and main ducts sized to the transport velocity with Darcy friction and fitting losses, the static-pressure balance at every junction by the balance-by-design (velocity pressure) method with the flow-ratio correction or by the blast-gate method, the air cleaner, the fan total and static pressure and power, and the stack exit velocity and height checks. A second part gives dilution ventilation: the steady-state and transient concentration for a contaminant generation rate, the flow for an exposure limit, the purge time, the lower-explosive-limit dilution and the flow to carry off sensible heat; a third part balances the makeup air and its heating load.

1 worked example reproduced, listed on the tool page.

Other Building Systems sections

HVAC Loads · Ducts and Airflow · Psychrometrics · HVAC Equipment · Energy · Plumbing · Fire Protection · Lighting and Electrical · Controls and Commissioning · Codes and Compliance