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
Chapter 5–Laboratory Facility Exhaust Systems
Fire Dampers
Though normally required where ducts pass through fire rated construction (fire
walls), NFPA 45 states that laboratory exhaust systems shall not be equipped with
fire dampers. The intent is to ensure against stoppage of the exhaust airflow even if a
fire is present. This is in agreement with more advanced fire protection engineering
and smoke control technology. However, since some local codes require fire
dampers, be sure to resolve this issue before configuring the exhaust system without
fire dampers.
Maintenance Access
Laboratory exhaust system fans and plenums should be readily available for
servicing and preventive maintenance. For maximum protection against worker
exposure or leakage of exhaust into the building, the fans should be located on the
roof of the building. Exhaust system interior ductwork runs should be accessible for
inspection and possible replacement. Each control device such as a damper and its
operator should also be accessible for periodic inspection and service. In particular,
airflow measurement stations should allow easy access for periodic testing, re-
calibration and/or service replacement.
Specialty Exhaust Systems
Perchloric Acid Fume Hoods
Perchloric acid fumes present a special hazard due to their extreme corrosiveness
and the explosive potential of perchlorate salts that condense in the exhaust ducts.
For these reasons a perchloric acid fume hood is normally operated as a constant
volume fume hood with its own individual exhaust system. Only two types of
materials are suitable for perchloric fume hood exhaust systems – Type 316
stainless steel or PVC. However, since building codes normally require PVC ducts to
be enclosed within a 2-hour fire rated wall enclosure, this makes a PVC perchloric
exhaust system more expensive and harder to implement than stainless steel.
Additionally, no organic (carbon-based) compounds such as rubber can be used in a
perchloric acid exhaust system. Neoprene should be used for all seals.
A perchloric acid exhaust system should consist of a minimum amount of fittings,
bends, and especially horizontal runs to minimize the locations where perchlorate
salts may settle out. The exhaust system must be air and water tight and be
equipped with a water washdown system to enable the entire exhaust system, from
the stack exit back down to the fume hood to be washed down after each day's use.
Exhaust fans are normally constructed of PVC material and all wiring and electrical
devices which are part of the fume hood and the exhaust system must be UL listed
as intrinsically safe per UL 916.
38 Siemens Building Technologies, Inc.