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
Proper Exhaust System Functionality
Proper Exhaust System Functionality
Fume hoods, biosafety cabinets, and other specialty exhaust provisions (snorkels,
canopy hoods, etc.) within a laboratory room rely on the adequacy of the exhaust
system to achieve their functionality. Without a properly functioning exhaust system
these devices can do little to protect the user. Proper exhaust system functionality in
turn basically translates into maintaining the proper level of negative static pressure
(sometimes referred to as the suction or vacuum effect) that is created in the system
by the exhaust fans.
For a centralized laboratory exhaust system to achieve proper functionality, the
exhaust system must maintain the proper level of negative static pressure in all
laboratory rooms. This requirement applies to all types of central exhaust systems
whether they are part of a constant volume or variable volume ventilation system.
Too little negative static pressure will not provide sufficient ventilation system exhaust
airflow from the fume hoods and other exhaust provisions. Too much negative static
pressure will cause excessive exhaust airflow and can induce harmful turbulence
particularly in constant air volume systems that have no local control over the static
pressure or exhaust airflow. Thus, too little and too much exhaust airflow can
adversely affect the proper functionality of containment units and result in inadequate
protection for laboratory workers against exposure to harmful substances.
Excessively high exhaust airflow rates will likely create very objectionable airflow
noise throughout a facility and result in excessive ventilation system energy
consumption.
Whether the facility has constant volume or variable volume ventilation systems, a
means should be provided to control the negative static pressure, especially in
centralized exhaust systems. Without control, the static pressure level in the exhaust
system will vary as a result of activities occurring throughout the facility. When
exhaust systems do not have effective static pressure control and static pressure
variation is occurring, it becomes a very difficult and sometimes nearly impossible
task to properly set up and adjust individual laboratory room ventilation and
containment unit airflow’s. Making an airflow adjustment to a single containment unit
results in a change in the exhaust system static pressure which in turn will affect the
rooms and other containment units that have previously been adjusted. This results
in a continuous cycle of checking, testing and re-adjusting individual room and
containment unit exhaust airflow’s and then repeating the process again and again.
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