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
Containment Units
BYPASS
AREA
MOVABLE
SASH
100% OPEN
SASH
50% OPEN
SASH
CLOSED
SASH
@ MAXIMUM CFM
EXHAUST AIR
@ APPROX. 97%
EXHAUST AIR
@ APPROX. 95%
EXHAUST AIR
Figure 7. Constant Air Volume Bypass Fume Hood Showing How the Bypass Area
Attains a Nearly Constant Exhaust Airflow Regardless of Sash Position.
• HOPEC constant volume fume hoods–An energy limiting approach that
has applied to constant volume fume hoods is termed the HOPEC fume
hood. The HOPEC (hand operated positive energy control) type of fume
hood is a “hybrid” type of fume hood that is offered by some suppliers. It is
basically a constant volume bypass fume hood with a design that provides
normal access to experimental or test apparatus inside when the sash is no
more than about half open. This is attained by the use of a combination
vertical rising and a horizontal sliding sash and also utilizing a vertical sash
stop at the 18 inch height.
In normal use, while an experiment or test is active, the HOPEC sash
arrangement allows the user sufficient access to manipulate the apparatus
inside the fume hood. But since the sash opening is no more than about 50%
of maximum, fume hood air consumption is held down to about half of what it
would be with a regular constant air volume bypass fume hood.
When necessary to obtain full access to the fume hood interior (as when
setting up or dismantling apparatus), the sash can be fully opened, but the
fume hood exhaust airflow remains unchanged. This will result in an average
face velocity of around 60 fpm. Although this face velocity is generally too
low for occupant protection when the fume hood is in active use and fumes
are being generated, it is acceptable when accessing the inside for setup or
dismantling purposes only
9
.
9
The user must understand the provisions of this type of fume hood and be aware that all experimental activity and the
generation of hazardous fume must be terminated before fully opening the sash and any dismantling is undertaken.
Siemens Building Technologies, Inc. 49