Definitions

For the purposes of this standard, the following definitions are applicable.

3.1 acceptable ceiling concentration: (ACC). The desig­
nated level of an air contaminant to which an employee may
be exposed at any time during an 8-hour shift, except for a
specified time period and up to a specified concentration not
exceeding the "acceptable maximum peak concentration"
above the acceptable ceiling concentration for an 8-hour
shift. Refer to 29 CFR 1910.1000 and Appendix A, Par. A.2.

3.2 breathing zone: A hemisphere forward of the shoul­
ders with a radius of 6 to 9 inches. Refer to OSHA Instruc­
tion CPL 2-2.20A, March 30,1984; amended by CPL 2-20A
CH-1, October 29,1984.

3.3 continuous hydrogen sulfide monitoring equip­
ment: Equipment capable of continuously measuring and
displaying the concentration of hydrogen sulfide in ambient
air.

3.4 emergency response planning guide—level 2:

(ERPG-2). The maximum airborne concentration below which it is believed that nearly all individuals could be ex­posed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms that could impair an individual's ability to take protective actions. Refer to Technical Guidance for Hazards Analysis; Emer­gency Planning for Extremely Hazardous Substances.

3.5 enclosed facility: A three-dimensional space enclosed
by more than two-thirds (²/j) of the possible projected plane
surface and of sufficient size to allow the entry of personnel.
For a typical building, this would require that more than two-
thirds of the walls, ceiling, and floor be present. Refer to API
Recommended Practice 500.

 

provide proper and prudent safe operations activities and those required to effect control of the hazardous hydrogen sulfide or sulfur dioxide conditions.

3.7 gas detection instrument: An assembly of electrical,
mechanical, and chemical components designed to sense and
respond continuously to the presence of chemical gases in at­
mospheric mixtures.

3.8 hydrogen sulfide: Chemical formula is H₂S. A
flammable, toxic gas that is heavier than air and sometimes
found in fluids encountered in oil and gas producing and gas
processing operations. Inhalation at certain concentrations
can lead to injury or death. Refer to Appendix A.

3.9 immediately dangerous to life and health: (IDLH).
An atmospheric concentration of any toxic, corrosive, or as­
phyxiant substance that poses an immediate threat to life or
would cause irreversible or delayed adverse health effects or
would interfere with an individual's ability to escape from a
dangerous atmosphere. The National Institute for Occupa­
tional Safety & Health (N1OSH) considers 300 ppm and 100
ppm to be the IDLH concentrations for hydrogen sulfide and
sulfur dioxide, respectively. API Publication 2217A specifies
an oxygen content of less than 19.5% as oxygen deficient
and an oxygen content of less than 16% is considered IDLH.

3.10 inadequately ventilated: Ventilation (natural or ar­
tificial) that is not sufficient to prevent the accumulation of
significant quantities of hydrogen sulfide-air mixtures in ex­
cess of 10 ppm.

3.11 length-of-stain detector: A specially designed pump
and colorimetric indicator tube detector (length-of-stain),
with a supply of detector tubes, that operates by using the
pump to pull a known volume of air or gas through a detector
tube. The tubes contain chemical reagents that are designed
to detect the presence and display the concentration of hy­
drogen sulfide or sulfur dioxide in the sample. The length of
the resultant color band in the tube indicates an instanta­
neous quantitative concentration of the specific chemical in
the sample.

3.12 permissible exposure limit: (PEL). The designated
level of any airborne contaminant to which an employee may
be exposed. The PEL may be expressed as an eight-hour
time weighted average (TWA), a ceiling value, a short term
exposure level (STEL), or a skin designation. PELs are sub­
ject to change and users should check the latest version of 29
Code of Federal Regulations Part 1910.1000 for compliance.

3.13 shall: Indicates the "recommended practice(s)" has
universal applicability to that specific activity.

shclter-in-place: The concept of providing the public
additional protection by having residents stay indoors until
emergency evacuators arrive or the emergency is over. Refer
to references 62,63, 64, 65, 66, and 67

3.15 should: Denotes a "recommended practice(s)" 1)
where a safe comparable alternative practice(s) is available;
2) that may be impractical under certain circumstances; or 3)
that may be unnecessary under certain circumstances.

3.16 sulfur dioxide: Chemical formula is SO₂. A toxic
product of combustion of hydrogen sulfide. This gas is heav­
ier than air. Inhalation at certain concentrations can lead to
injury or death. Refer to Appendix B.

3.17 threshold limit value: (TLV). The maximum air­
borne concentration of a substance to which, it is believed
that, nearly all workers may be repeatedly exposed day after
day without adverse effects, as determined by the responsi­
ble committees of the American Conference of Governmen­
tal Industrial Hygienists (ACGIH). Refer to "Threshold
Limit Values and Biological Indices. "TLV" is a trademarked
term of ACGIH. TLVs are subject to change and users
should check the latest edition of the forestated reference.