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
Chapter 4–Ventilation Systems
Classification
Chapter 4 discusses the various classes of ventilation systems. It includes the following
topics:
• Types of ventilation systems
• VAV systems
• Choice of ventilation system
Types of Ventilation Systems
Ventilation systems for virtually any application can be classified into two general categories:
constant air volume (CAV) or variable air volume (VAV). The constant air volume type of
ventilation system is by far the most prevalent type of system in use today. However, the
variable air volume type of system is becoming popular, particularly in new facility
applications because it offers the advantages of greater operational flexibility and the
opportunity for the greatest reduction in energy usage.
CAV Systems
As the name implies, a constant air volume type of ventilation system always provides a
relatively constant amount of ventilation airflow or cfm. The amount of airflow is selected
during the ventilation system design and is based upon satisfying a room’s minimum
ventilation requirements and whatever additional airflow might be necessary to handle worst
case room comfort conditioning and any other special requirements. From the time this type
of system is placed in operation, the airflow rate is typically never changed unless a major
facility renovation takes place. While basically simple in function, the CAV system’s major
drawback is that it consumes a high amount of energy since it has no provision to allow
reducing the ventilation rate when permissible as during unoccupied times. Figure 1
illustrates a typical CAV ventilation system applied to a laboratory room having chemical
fume hoods. With reference to Figure 1, a constant volume of outside air is drawn into the
primary air handling unit where it is filtered and conditioned (heated or cooled and humidified)
in accord with the needs of the facility for at a given time of the year. A constant volume of
conditioned air (normally at a cooler temperature than room air) is supplied throughout an
entire facility or a portion of a larger facility. The temperature of the air that is supplied to an
individual laboratory room is raised by a room terminal unit reheat coil as may be necessary
to meet occupant comfort and other needs of the specific room.
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