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
Exhaust System Expansion
Although various configurations of centralized exhaust systems are possible, it is
advisable to always incorporate at least two exhaust fans in each system to enhance
the safety and reliability. This ensures that failure of one fan does not result in a total
exhaust system failure. Additionally, it is preferable for at least two exhaust fans to be
running at all times as the normal operational mode of the exhaust system. Should
one fan fail, this arrangement will prevent total loss of system exhaust even for a
short time. In contrast, having the second fan as a standby fan arranged to start
when needed will usually provide adequate continuity of system operation since it will
require considerable time before it can reach operational speed. There is also less
assurance that a standby fan that has been off for an extended period of time will
automatically come on line as intended.
To ensure having a very reliable central exhaust system, the normally operating fans
should also be supplemented with at least one extra standby fan. This not only helps
to swiftly restore full operational capacity to the exhaust system in case of a single
fan failure, but also allows periodic inspection and preventive maintenance on all
fans on a rotating basis without having to reduce the number of operating fans.
Exhaust System Expansion
The design and configuration of a centralized exhaust system should be done with
regard to the potential need for future system expansion. For instance, the exhaust
system may need to have additional branch ducts added to accommodate new
laboratory containment units and other local exhausts. In particular, this will require
the exhaust fans to be capable of handling an increased amount of exhaust system
airflow and providing increased negative (suction) pressure. It will also require
operating the fans at a higher speed which in turn requires that the fan motors be
capable of the increased power requirements. Thus, both the fans, motors, and
power feeds should be initially sized with consideration to anticipated future
expansion. Aside from attaining additional exhaust airflow capacity from the existing
system components, a worthwhile consideration would be to allow space to add at
least one additional exhaust fan to the system.
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