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SEMI F6-92 © SEMI 19 92 3 6.3 Those substances that fall into t h e following categories: 6.3.1 Any HPM’s which have a mat e r ia l hazard index (MHI) valu e equal to or greater than 500,00 0. 6.3.2 Highly to xic ga s. 6…

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SEMI F6-92 © SEMI 1992 2
4.2 controlled work area — A spa ce within a building
where HPM’s may be stored, handled, dispensed, or
used.
4.3 equilibrium vapor concentration (EVC) — The
state of a material at which vapor pressure has
stabilized and is no longer rising or falling. The EVC
value (in parts per million) of a material is determined
by multiplying the vapor pressure by 10
6
and dividing
by atmospheric pressure (760 mmHg at sea level).
4.4 hazardous production material (HPM) — A solid,
liquid, or gas that has a degree-of-hazard rating in
health, flammability, or reactivity of Class 3 or 4 as
ranked by NFPA 704 and that is used directly in
research, laboratory, or production processes that have
as their end product materials that are not hazardous.
4.5 highly toxic gas — A chemical that has a median
lethal concentration (LC
50
) in air of 200 parts per
million by volume or less of gas or vapor, or 2
milligrams per liter or less of mist, fume, or dust, when
administered by continuous inhalation for one hour (or
less if death occurs within one hour) to albino rats
weighing between 200 and 300 grams each.
4.6 immediately dangerous to life and health (IDLH)
— A concentration of airborne contaminants, normally
expressed in parts per million or milligrams per cubic
meter, which represents the maximum level from which
one could escape within thirty minutes without any
escape-impairing symptoms or irreversible health
effects. This level is established by the National
Institute of Occupational Safety and Health (NIOSH).
4.7 level of concern (LOC) — Equal to 0.1 of the
IDLH value.
4.8 lower detectable limit of instrument (LDL) — The
lowest concentration of a substance that will give an
instrument response with a signal-to-noise ratio of at
least 3 db.
4.9 material hazard index (MHI) — A numeric value
used for ranking chemical production materials in order
to determine the level of controls necessary for
regulation. MHI is determined by dividing the
equilibrium vapor concentration (EVC) of a material at
25°C by the level of concern (LOC) value for the
material.
4.10 open secondary containment — Secondary
containment with an open-ended annular space. This
annulus must be directed to a system designed to handle
the contained HPM.
4.11 permissible exposure limit (PEL) — The
maximum permitted eight hour time-weighted average
concentration of an airborne contaminant. The
maximum permitted time-weighted average exposures
to be used are those published in 29 CFR 1910.1000.
4.12 pressure decay method — The method of
detection of leakage through pressure loss, over a
period of time, within a vessel or piping system.
4.13 primary containment — The first level of
containment (i.e., the inside portion of the container
that comes into immediate contact on its inner surface
with the material being contained).
4.14 pyrophoric — Capable of spontaneous ignition in
air at or below a temperature of 54.5°C (130°F).
4.15 secondary containment — Level of containment
that is external to and separate from primary
containment. Secondary containment is a method of
safeguarding used to prevent unauthorized releases of
toxic or hazardous gases into uncontrolled work areas.
Secondary containment means those methods or
facilities in addition to the primary containment system.
4.16 threshold limit value/time-weighted average
(TLV/TWA) — As defined by the American Conference
of Governmental Industrial Hygienists (ACGIH).
4.17 uncontrolled work area — Any area outside of a
secondary containment system where people are likely
to be present.
4.18 vacuum decay method — Leakage detection
determined by the loss of vacuum (increase in
pressure), over a period of time within a vessel or
piping system.
5 Containment Function
5.1 Secondary containment should, in case of release,
segregate the hazardous production material (HPM)
from the surrounding area.
5.2 Secondary containment systems should include
provisions to contain and detect substances which pose
health or property hazards and to direct such substances
into areas or facilities that can safely treat, dispose of,
or dilute them prior to release into the atmosphere.
6 Containment Application
Secondary containment may be used on any system if
deemed appropriate by the authority responsible for the
system. Secondary containment should be mandatory
for all HPM’s that are included in the following
categories:
6.1 Those substances with threshold limit values
(TLV) below the lower detectable limit (LDL) of the
detection systems in use.
6.2 Those substances that provide inadequate warning
properties.
SEMI F6-92 © SEMI 19923
6.3 Those substances that fall into the following
categories:
6.3.1 Any HPM’s which have a material hazard index
(MHI) value equal to or greater than 500,000.
6.3.2 Highly toxic gas.
6.3.3 Pyrophorics.
6.3.4 Substances with unknown, but potentially high
toxicities (e.g., organometallics).
6.3.5 Materials with an NFPA 704 reactivity rating of
3 or 4.
6.3.6 Any corrosives that are not contained in inert
process piping.
6.4 Where piping containing HPM ’s is installed in a
manner to conceal it from view.
6.5 Where piping containing HPM ’s is installed in
uncontrolled or unventilated areas such as drop ceilings
or behind walls.
6.6 Where required by UBC H-6 or other existing
codes.
6.7 Where there is any reasonable possibility of a leak
in the primary containment due to normal wear and
tear, possible abuse, or corrosive attack to the piping on
the inside or exterior.
7 Containment Methods
The method of containment may take many forms
provided that the method is sound in engineering
design. This design should be in conformance to
nationally recognized codes and standards as well as to
the requirements of local safety jurisdictions.
8 Materials of Construction
8.1 Chemical Compatibility — If there is a possibility
that the HPM, or its reaction products, is corrosive, to
any extent, to the secondary containment, one should
develop a procedure to verify the integrity of the
containment system. This verification procedure need
only be performed in the event that the HPM, or its
reaction products, contacts the containment (see Section
9).
8.2 Fire Resistance — If walls are used as the
secondary containment system, they should be
constructed of materials resistant of fire. The fire rating
of the secondary containment should be as follows:
8.2.1 Two hour rating for pyrophorics;
8.2.2 One hour rating for all others.
9 Design Requirements
9.1 Design Pressure — The system should be
designed to provide secondary containment with the
ability to withstand the pressure of the entire volume of
the potential leaking source without leakage.
9.1.1 Closed secondary containment systems should
have sufficient design pressure to withstand the
pressure of the entire contents of the source of the
HPM. The design safety factor must be consistent with
ANSI B31.3.
9.1.2 Open secondary containment systems should
have sufficient design pressure to withstand the release
at full tank pressure or the entire contents of the HPM
released within a time of two minutes.
9.1.3 Special consideration should be given to the
containment of pyrophorics. Some pyrophorics can
develop considerable explosive pressure. The
elimination of oxygen from the annulus of a
containment system should be considered in lieu of
explosive pressure data.
9.2 Resistance to External Forces — The method of
construction of secondary containment systems should
be sufficient to withstand:
9.2.1 Normal physical abuse found in the industrial
workplace.
9.2.2 Seismic zone activity as shown in the UBC
(Uniform Building Code) or other applicable codes.
9.3 Leak Integrity — The system should be designed
to provide secondary containment with sufficient leak
integrity to prevent exceeding the PEL of the HPM in
uncontrolled work areas.
9.3.1 Primary piping should be leak tested in
accordance with SEMI F1.
9.3.2 Closed secondary containment systems should
have the same leak integrity as the primary containment
except the closed secondary containment systems
should be leak tested with the annulus pressurized to 2
times the maximum operating pressure with argon
containing at least 10% helium. There should be no
drop in pressure for a period of 12 hours.
9.3.3 Open secondary containment systems should be
leak tested to the same criteria as closed secondary
containment systems per 9.3.2 above.
10 Separation of HPM’s
A single secondary containment may be used to contain
more than one HPM provided that those HPM’s are not
reactive with any other HPM in the common
containment. Documents that should be considered for
proper separation of HPM’s include:
SEMI F6-92 © SEMI 1992 4
10.1 SEMI S4, Safety Guideline for the
Segregation/Separation of Gas Cylinders Contained in
Cabinets
10.2 Materials Safety Data Sheets
10.3 NFPA Fire Protection Guide on Hazardous
Materials
11 Cross Connections
There should be no mechanical cross connection of
secondary containment systems with other systems not
designed specifically for the secondary containment of
the particular HPM’s.
12 Monitoring
The annulus should be monitored for leakage of the
primary system in accordance with the following:
12.1 The sensitivity of the detection system should be
sufficient to detect leakage at 1/2 Threshold Limit
Values (TLV’s) at the discharge to treatment of an open
secondary containment system.
12.2 Detection of leakage into the annulus of the
secondary containment system should include alarm
systems.
12.3 Detection methods may include:
12.3.1 Direct detection of the HPM or its reaction
products (open secondary containment system).
12.3.2 Pressure decay method (closed secondary
containment system).
12.3.3 Vacuum decay method (closed secondary
containment system).
13 Leak Management
The secondary containment system should be designed
to control and direct leaking materials. Control of
HPM’s may consist of dilution, absorption,
incineration, scrubbing, venting, or those methods
deemed safe and suitable to the governing authorities
responsible for the facility. The initiation of the
secondary containment alarm system should be
automated. This system should automatically institute
the management of the leaking HPM in the event of a
breach of the primary system.
14 Periodic Testing - After In stallation
14.1 Secondarily contained piping systems must be
inspectable. The method of inspection must be able to
reveal the current strength and leak integrity of the
primary and secondary containment systems.
14.2 The secondary containment must be periodically
leak tested in accordance with the criteria set forth in
Section 9.3 of the above. Structural testing of both the
process piping and the secondary containment should
be conducted to the maximum pressure specified in
Section 9.1 of the above.
14.3 Any secondarily contained piping system failing
the periodic inspection should be repaired or replaced
immediately.
NOTICE: These standards do not purport to address
safety issues, if any, associated with their use. It is the
responsibility of the user of these standards to establish
appropriate safety and health practices and determine
the applicability of regulatory limitations prior to use.
SEMI makes no warranties or representations as to the
suitability of the standards set forth herein for any
particular application. The determination of the
suitability of the standard is solely the responsibility of
the user. Users are cautioned to refer to manufacturer’s
instructions, product labels, product data sheets, and
other relevant literature respecting any materials
mentioned herein. These standards are subject to
change without notice.
The user’s attention is called to the possibility that
compliance with this standard may require use of
copyrighted material or of an invention covered by
patent rights. By publication of this standard, SEMI
takes no position respecting the validity of any patent
rights or copyrights asserted in connection with any
item mentioned in this standard. Users of this standard
are expressly advised that determination of any such
patent rights or copyrights, and the risk of infringement
of such rights, are entirely their own responsibility.
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