Basic Documentation
Table Of Contents
- About this Application Guide
- Chapter 1–Introduction
- Chapter 2–Goals of the Laboratory Environment
- Chapter 3–Unique Ventilation Needs of a Laboratory Facility
- Chapter 4–Ventilation Systems Classification
- Chapter 5–Laboratory Facility Exhaust Systems
- Chapter 6–Laboratory Containment Units - Ventilation
- Chapter 7–Room Ventilation, Makeup Air, and Pressurization Control Systems
- Chapter 8–Laboratory Temperature and Humidity Control Systems
- Chapter 9–Laboratory Emergencies - Ventilation System Response
- Chapter 10–Laboratory Ventilation System - Validation
- Chapter 11–Laboratory Ventilation System - Commissioning
- Glossary
- Index
Glossary
direct digital control (DDC)
(1) Industry-standard term for intelligent, microprocessor-based control units in various
locations throughout a facility. It may incorporate P, PI, or PID control. (2) Electronic
controller that is programmed to provide the required control action. Differs from an analog
controller in that the digital controller initially applies a numerical value to the incoming signal
from a sensor (digitizes the input). This enables the signal to be processed by the controller
program. A digital controller program thus follows the mathematical and logical thought
process of the control program designer to arrive at the required control output signal.
face velocity
Average air velocity through the face of the fume hood. The speed or velocity of air entering a
biological safety cabinet or a fume hood through the sash opening. Although commonly
called face velocity, average face velocity is more accurate since the face velocity actually
varies throughout the plane of the sash opening. The rate of 100 feet per minimum (fpm) is
the most commonly referenced (and required) average face velocity for a fume hood. (Note:
100 feet per minute is roughly equivalent to a little more than 1 mile per hour.)
fan curve
Graph showing the cubic feet per minute (cfm) produced by a fan at a specific revolutions per
minute (rpm) and static pressure measured across the fan. Fan curves indicate a fan’s
performance as the airflow through a ventilation system meets varying resistance. Fan
curves are necessary when designing ventilation systems in order to select the optimum fan
size, revolutions per minute (rpm), and motor horsepower to produce the desired airflow and
static pressure required in a ventilation system. Also called fan performance curve. See
System Effect Factor.
feedback
Measurement of the process variable being controlled, such as airflow and temperature,
pressure, that a sensor provides to a controller. The controller always has instant feedback of
the actual results of its control action and enables the most precise and accurate type of
control.
flow tracking
Maintaining a positive or negative static pressure of a room with respect to an adjoining
room, corridor, or the outside of the building. Flow tracking consists of always maintaining a
fixed amount of airflow difference between the total supply air and total exhaust air from a
room. Although the specific airflow cubic feet per minute (cfm) of the supply and exhaust may
change, airflow tracking generally maintains a fixed cfm differential. By maintaining more
supply airflow than exhaust, a room is maintained at a positive static pressure. By
maintaining less supply airflow than exhaust, a room is maintained at a negative static
pressure. Also called airflow tracking.
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