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Alberta Legislation

H2S - Hydrogen Sulphide (also called 'sour gas', 'sewer gas')

This is not an official source of information. It has been assembled as a convenience to students for reference and further study. Some extracts from official sources such as Regulations are provided. These are not guaranteed to completely cover all the material available in the Regulations. URL's of those official sources are provided to allow the full text to be consulted.
Other sources of Hydrogen Sulphide Safety information for Alberta:

Occupational Heath and Safety Code 2009:
Part 37 Explanation Guide - OIL & GAS WELLS


Hydrogen Sulphide at the Work Site


The following is © 1995 - 2010 Government of Alberta.
Hydrogen sulphide code of practice required, 26, Schedule 1, Table 1. OEL, Schedule 1, Table 2

Worker participation
8(1) An employer must involve affected workers in the hazard assessment
and in the control or elimination of the hazards identified.
8(2) An employer must ensure that workers affected by the hazards identified
in a hazard assessment report are informed of the hazards and of the methods
used to control or eliminate the hazards.

Codes of practice
26(1) An employer must have a code of practice governing the storage,
handling, use and disposal of a substance listed in Schedule 1, Table 1 that is
present at a work site
(a) as pure substance in an amount exceeding 10 kilograms, or
(b) in a mixture in which the amount of the substance is more than
10 kilograms and at a concentration of 0.1 percent by weight or more.
26(2) The code of practice must include measures to be used to prevent the
uncontrolled release of the substance and the procedures to be followed if there
is an uncontrolled release.
Part 37 Oil and Gas Wells

750 This Part applies to activities and auxiliary processes associated with
exploring for and drilling, operating or servicing wells for gas, crude oil or
geothermal energy.

Competent supervisor
751(1) An employer must appoint a supervisor to supervise an exploration,
drilling, servicing, snubbing, testing or production operation.
751(2) An employer must ensure the supervisor is competent in each of the
following that is within the supervisor's area of responsibility:
(a) safe work practices, including the safe operation of a plant at the work
(b) the safe handling, use and storage of hazardous substances;
(c) well control and blow out prevention;
(d) detecting and controlling worker exposure to hydrogen sulphide;
(e) handling, using, maintaining and storing personal protective
(f) appropriate responses to emergencies at the work site;
(g) the duties and responsibilities of all workers supervised by the
(h) training workers supervised by the supervisor in safe work practices
and procedures;
(i) health and safety programs.

Breathing equipment
752(1) If a worker is undertaking emergency response activities at a well site and
the worker may be exposed to a harmful substance in excess of its occupational
exposure limit, an employer must ensure that sufficient self-contained breathing
apparatus units that comply with section 251 are provided, based on the hazard
assessment required by Part 2 and the emergency response plan required by
Part 7.
752(2) Despite subsection (1), if there is only one worker at the well site, an
employer may use alternate means to protect the worker to ensure that the
worker is not exposed to a harmful substance in excess of its occupational
exposure limit.

Drill stem testing
779(1) This section applies to drill stem testing operations.
779(2) An employer must ensure that after fluids are encountered while tripping
out, workers use the mud can and test plug on every joint of pipe disconnected,
unless the drill stem contents have been pumped out and replaced with drilling
779(3) An employer must ensure that
(a) workers test for the presence of hydrogen sulphide and hydrocarbons
if oil, water or gas is encountered during the drill stem testing, and
(b) if hydrogen sulphide is present, the sour fluids in the drill stem are
displaced with drilling fluid and circulated to a flare pit or a holding
tank that is at least 50 metres from the well.

Schedule 1 Chemical Substances
Table 1 Substances and processes requiring a code of practice

[See subsection 26(1)]

• Hydrogen sulphide
Table 2 Occupational exposure limits for chemical substances
(1) A person using this Table may apply either the "mg/m3" or "ppm" measure defined as follows:
"mg/m3" means milligrams of substance per cubic metre of air measured at ambient work site conditions;
"ppm" (parts per million) means parts of a vapour or gas by volume at standard conditions (25oC and an absolute barometric pressure of 101.3 kilopascals) per
parts of contaminated air by volume at ambient work site conditions.

(2) "f/cc" means fibres per cubic centimetre of air; "CAS" means Chemical Abstracts Service.

(3) The numbers 1, 2 and 3 in the "Substance Interaction" column have the following meanings:
1 - substance may be readily absorbed through intact skin;
2 - substance is a simple asphyxiant that may create an atmosphere deficient in oxygen; available oxygen in the range of 19.5 percent to 23 percent by
volume must be present.
3 - occupational exposure limit is based on irritation effects and its adjustment to compensate for unusual work schedules is not required.

(4) A carcinogen is defined as "an agent capable of inducing benign or malignant neoplasms." Based on the weight of evidence from epidemiologic studies, "A1"
would be a Confirmed Human Carcinogen and means that the agent is carcinogenic to humans. "A2" would be a Suspected Human Carcinogen and means that human data are accepted as adequate in quality but are conflicting or insufficient to classify the agent as A1 (American Conference of Governmental Industrial Hygienists).

Schedule 1

Substance CAS Number 8-hour

Occupational exposure

Ppm mg/m3 f/00

Hydrogen sulphide 7783-06-4 10 14 -

15-minute or ceiling c
occupational exposure limit
Ppm mg/m3
(c) 15 (c) 21

Oil Sands Conservation Act

Pollution control and safety
6 Unless the Board otherwise approves, the operator of an oil sands site producing gas with a hydrogen sulphide content of greater than 10 moles per kilomole, or any lower hydrogen sulphide content that the Board may by order stipulate, shall burn the gas using an incinerator approved by the Board or through a flare line that terminates with a vertical riser of at least 12 metres, or such greater height as the Board considers necessary and is provided with a suitable guard to prevent wind from extinguishing the flame, a suitable pilot and an ignition device to ensure continuous ignition, if
(a) a flare line is installed for routine flaring or burning of gas during normal operations,
(b) a pressure relief valve, rupture disk or burst plate is installed on a separator or other pressure vessel, or
(c) gas is discharged during any test, cleaning or servicing operation.

Precautions re hydrogen sulphide gas
7(1) The operator of an oil sands site handling gas with a hydrogen sulphide content that exceeds 10 moles per kilomole, or any lower hydrogen sulphide content that the Board may by order stipulate,
(a) shall erect signs, as specified by the Board, at the entrance to the site warning of the presence of poisonous gas, and
(b) shall not discharge or permit to be discharged to the atmosphere stock tank vapours or any other gas produced from the well, other than steam vapours from an open tank, unless they are burned so that essentially all sulphur compounds are converted to sulphur dioxide, ensuring that the average concentration of hydrogen sulphide and sulphur dioxide in the ambient air does not exceed the maximum permissible concentrations as determined by the Department of Environment.
(2) Gas discharged pursuant to subsection (1)(b) shall be burned in accordance with section 6.
(3) The Board, on application, may exempt an operation from any provision of this section where, in the opinion of the Board, the nature of the production, remoteness of the area or other circumstances warrant the exemption.

Emergency response plan
8 The operator of an oil sands site shall, when requested to do so by the Board, file with the Board an emergency response plan that will be followed
(a) when handling gas with a hydrogen sulphide content greater than 10 moles per kilomole, or any lower hydrogen sulphide content that the Board may by order stipulate, or
(b) in the event of an uncontrolled emission of contaminants to the air, water or land.

Part 5 Processing Plant
Storage or disposal
48 For the purpose of energy resource conservation, an operator shall apply for and obtain the approval of the Board for the storage or disposal of any oil sands, coke, sulphur, precipitator ash or other hydrocarbon effluent or discard associated with the processing plant.

Operation of processing plant
49 Unless the Board otherwise approves, the operator shall carry out operations in a manner that, under normal operating conditions, will
(d) maximize the gathering and utilization of gas produced,
(e) maximize the gathering of gaseous mixtures containing hydrogen sulphide for delivery to the sulphur recovery plant,
(f) maximize the recovery of sulphur contained in the hydrogen sulphide delivered to the sulphur recovery plant,

Discharge of gas to atmosphere
51 Unless the Board otherwise approves, the operator of a processing plant shall not discharge or permit to be discharged any gas containing hydrogen sulphide, unless it is burned so that essentially all of the sulphur is converted to sulphur dioxide.

Content of monthly statement
57(1) Unless the Board otherwise directs, an operator producing hydrogen sulphide or other sulphur compounds shall file with the Board, on or before the 22nd day of each month, statements of monthly and, if required by the Board, daily totals of plant input and output for the preceding calendar month in the form of a processing plant sulphur balance and a sulphur plant sulphur balance including, where applicable,
(a) volumes of raw gas and crude bitumen,
(b) hydrogen sulphide content of the raw gas determined at a frequency specified by the Board,
(c) sulphur content of the crude bitumen,
(d) sulphur content of oil sands products,
(e) quantity of sulphur produced,
(f) quantity of sulphur in discard,
(g) sulphur recovery efficiency of the sulphur plant, and
(h) volume of sweet gas added to any sour gas flares during flaring.


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