Basic Documentation

Fume Hoods
Siemens Industry, Inc. 33
Topic Requirement(s) Commentary
(Special
Purpose)
Perchloric
Acid
California OSHA – Division of Occupational Health & Safety (DOSH) Subchapter 7.
General Industry Safety Orders, Group 16. Control of Hazardous Substances,
Article 107. Dusts, Fumes, Mists, Vapors and Gases
5154.1. Ventilation Requirements for Laboratory-Type Hood Operations:
When perchloric acid is evaporated in laboratory-type hoods…. the materials of
construction shall be inert, smooth, and nonabsorbent. Organic polymers shall not be
used except for inert fluoropolymers, such as polytetrafluoroethylene [PTFE] and
tetrafluoroethylene-hexafluoropropylene copolymer [Teflon FEP], or similar
nonreactive material. The hood and exhaust system shall be washed down with water
for decontamination and prior to opening for maintenance.
Exception: Portable laboratory scrubbing apparatus for perchloric acid digestions may
be used in lieu of the special requirements of this paragraph
National Fire Protection Association, Standard NFPA 45, 2011
8.5.7 Flexible connectors containing pockets in which conveyed material can collect
shall not be used in any concealed space or where strong oxidizing chemicals (e.g.,
perchloric acid) are used.
8-11.1 Perchloric acid heated above ambient temperatures shall only be used in a
chemical fume hood specifically designed for its use and identified as follows:
FOR PERCHLORIC ACID OPERATIONS
Exception: Hoods not specifically designed for use with perchloric acid shall be
permitted to be used where the vapors are trapped and scrubbed before they are
released into the hood. (See also 12.1.2.5)
8.11.2 Perchloric acid hoods and exhaust ductwork shall be constructed of materials
that are acid resistant, nonreactive and impervious to perchloric acid.
8.11.3 The exhaust fan shall be acid resistant and spark resistant.
8.11.4 The exhaust fan motor shall not be located within the ductwork
8.11.5 Drive belts shall be conductive and shall not be located within the ductwork.
8.11.6 Ductwork for perchloric acid hoods and exhaust systems shall take the shortest
and straightest path to the outside of the building and shall not be manifolded with
other exhaust systems.
8.11.6.1 Horizontal runs shall be as short as possible, with no sharp turns or bends.
8.11.6.2 The ductwork shall provide a positive drainage slope back into the hood.
8.11.6.3 Ductwork shall consist of sealed sections.
8.11.6.4 Flexible connectors shall not be used.
8.11.7
Sealants, gaskets and lubricants used with perchloric acid hoods, ductwork and
exhaust systems shall be acid resistant and nonreactive with perchloric acid.
8.11.8 A water spray system shall be provided for washing down the hood interior
behind the baffle and the entire exhaust system.
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When perchloric acid is heated above
ambient temperature it gives off vapors which
can condense and form potentially explosive
perchlorates. In addition, other chemicals that
are known to have similar properties should
also only be used in a perchloric acid hood.
Perchloric acid hoods should be washed
down after each use.
Perchloric acid fume hoods and related
exhaust systems should always be separate
from other fume hoods and exhaust systems.
Due to the need to keep the exhaust system
short and direct, it is advantageous to locate
the laboratories that have perchloric acid
hoods just below roof level.
Along with type 316 stainless steel, type 1
PVC and ceramic coated materials may be
used for the exhaust system.