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
The outstanding advantage of a VAV system is that it makes possible a reduction in energy
usage during occupied as well as during unoccupied periods. (More specific details on
ventilation system energy usage will be provided later in this guide.) Figure 2 illustrates a
typical variable air volume ventilation system applied to a laboratory facility.
With reference to Figure 2, a sufficient volume of outside air is drawn into the primary air
handling unit where it is filtered and conditioned (heated or cooled and humidified) to meet
the needs of the facility throughout the year. Conditioned air (normally at a slightly cooler
temperature than room air) is then supplied throughout the portion of the facility that the
primary system serves. As the air is supplied to individual laboratory rooms, it passes through
the room’s VAV terminal unit which contains a means to modulate the amount of air supplied
to the room to meet actual needs. In addition, the temperature of the supply air can be raised
by the reheat coil in the room VAV terminal unit as necessary to meet room ambient needs.
As the supply air passes through and is exhausted out from the laboratory room, it provides
the required occupied or unoccupied room ventilation (ACH) rate. In the case where the room
has biological safety cabinets that are exhausted to the outside or chemical fume hoods, the
amount of supply air may needed to replace or make up for the air exhausted from these
units may exceed the amount of air needed to meet the required room ACH rate.
In the case of VAV chemical fume hoods as shown in Figure 2, note that each fume hood’s
exhaust is varied in proportion to the size of the fume hood sash opening. A fume hood
exhaust control arrangement with a modulating damper in each VAV fume hood’s exhaust is
provided for this purpose.
Applying a VAV ventilation system to ensure that only the actual amount of supply air needed
is provided thus provides a significant opportunity for a facility to minimize energy usage.
LABORATORY ROOM
REHEAT
COOLING HUMIDIFICATION
PRIMARY AIR HANDLING UNIT
FILTERING
OUTSIDE AIR
HEATING
SUPPLY
FAN
VARIABLE
SPEED FAN
ROOM VAV TERMINAL UNIT
VAV FUME HOODS
EXHAUST
SYSTEM
GENERAL
EXHAUST
Figure 2. VAV Ventilation System Applied to a Laboratory Facility.
16 Siemens Building Technologies, Inc.