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
Centralized Exhaust Systems with Constant Volume Fans
Variable air volume centralized exhaust systems are typically the best solution for
laboratory facilities that have perhaps 30 or more chemical fume hoods. Because the
turndown range (ratio of maximum to minimum) exhaust airflow in such facilities may
be substantial (4 to 1 ratios being common), the fan speed as well as the exhaust
plenum bypass damper are both controlled to maintain the desired negative static
pressure level. This will accommodate the wide range of facility exhaust airflow that
the system may need to handle. Controlling fan speed also ensures that the
minimum vertical exit stack velocity can be maintained under varying exhaust
airflow’s. Various numbers of fans may be utilized although each fan is generally
provided with its own stack or discharge provision. When conventional stacks are
used, the required diameter of the exhaust stack at the point of discharge is then
calculated as described in the following paragraphs.
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