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
Chemical Fume Hoods
A chemical fume hood is a ventilated enclosed workspace designed to protect the
user against exposure to fumes, vapors and gasses by maintaining a directional
airflow into the fume hood through the fume hood’s face opening. Chemical fume
hoods are used to protect laboratory workers when conducting a test procedure or
doing experimentation involving chemicals or gasses. The air entering the fume hood
along with the entrained contaminants is subsequently exhausted out.
Unlike biosafety cabinets, there is no standard classification that covers fume hoods
with regard to application, level of protection, or specific operational provisions.
Rather, fume hoods are differentiated mainly based on physical configuration and
intended application. The most common types being:
• Bench top–The most commonly applied fume hood. The work surface is at
work bench height and the front of the fume hood is equipped with a movable
sash to allow user access to the inside. Available widths vary from about a 3
to 8 feet.
• Walk-in–A fume hood without a work surface that extends down to the floor
and has a movable sash arrangement that allows full internal floor to top
internal access. Walk-in fume hoods are used where it is desired to utilize
larger equipment within the fume hood which may be on rollers or carts, as
well as taller items such as bottled gas cylinders. A worker must never walk-
in this type of fume hood when it is in active use. The walk-in provision is
only intended to allow setup and dismantling activities before and after active
use.
• Distillation–A type of fume hood with an interior working surface that
extends down to about 1-1/2 feet off the floor along with a movable sash
arrangement that extends down to the work surface. The additional vertical
space allows room for distillation equipment which typically requires more
height than is normally available in bench type fume hoods.
• Perchloric acid–A fume hood intended for use with perchloric acid.
(Perchloric acid cannot be utilized in a non-perchloric acid fume hood since
the vapors released form perchloric acid will from perchloric salt deposits in
the fume hood and connecting exhaust system ductwork. Perchloric salts are
very unstable and can explode if allowed to buildup.) A perchloric acid fume
hood is designed and intended for use with its own separate exhaust system
that incorporates a full water washdown arrangement to dissolve, dilute and
drain away any accumulated perchloric salts from the exhaust system and
fume hood.
• Radioisotope–A fume hood designed for the same use of radioisotopes
which is constructed of material that will not become radioactive and is
designed to prevent any radioactive particulate from accumulating in
crevasses, corners or joints.
Siemens Building Technologies, Inc. 45