1.0 PURPOSE
The purpose of this procedure is to ensure Nitro Construction Services employees are protected from adverse health effects due to exposure to hydrogen sulfide.
2.0 RESPONSIBILITY
The Project Manager shall ensure the full and effective implementation of this procedure. All employees shall follow the requirements sets forth in this procedure.
3.0 REFERENCES
OSHA Fact Sheet – Hydrogen Sulfide (10/2005)
4.0 PROCEDURE
4.1 The Project Manager shall obtain a copy of the owner/client’s site-specific contingency plans for Hydrogen Sulfide.
4.2 The Project Manager shall ensure all Nitro Construction Services employees are trained on the owner/client’s site-specific contingency plans as they relate to Hydrogen Sulfide.
4.3 All employees shall be able to recognize the characteristics of hydrogen sulfide, understand the serious nature of the hazard, and respond appropriately.
4.4 All employees, including administrative and supervisory personnel, shall attend training on hydrogen sulfide hazards and response. The training shall address the following:
4.4.1 Methods of recognition and the physical properties of hydrogen sulfide
4.4.2 The hazards associated with hydrogen sulfide
4.4.3 How to respond when hydrogen sulfide is present
4.4.4 Plant or client requirements for working around hydrogen sulfide
4.4.5 Emergency and evacuation information to include owner/client’s site-specific contingency plans
4.4.6 Limitations
4.4.7 The requirements of this procedure
4.4 The Project Supervisor shall coordinate with the Nitro Corporate Safety Director to develop task-specific work plans addressing respiratory protection and additional training before working in any environment where hydrogen sulfide exposure exceeds 20 parts per million.
4.5 Atmospheric monitoring equipment must be maintained at the job site where the potential for hydrogen sulfide exposure exists. Alarm type monitors shall be set to alarm at ten parts per million hydrogen sulfide.
4.5.1 If You are working where
– The known concentration of hydrogen sulfide is >5 and <10 parts per million, OR
– The potential for hydrogen sulfide exposure more than 5 parts per million is likely, OR
– An accident or emergency may result in immediately elevated concentrations greater than 5 parts per million
Then you must
– Monitor the area for airborne hydrogen sulfide each day before working in the area and maintain constant monitoring with an area monitor or personnel monitors with an automatic audible (or audiovisual) warning device set to alarm at 10 ppm for the duration of work each day.
4.5.2 If You are working in a location where
– The measured and/or potential exposure is less than 5 parts per million and is localized (an example is u-drains in a paper mill when no other source of hydrogen sulfide is in the immediate area)
Then
– Constant monitoring is not required.
4.5.3 If during work, an increased level of hydrogen sulfide is suspected due to:
– Employee symptoms, or
– Increased odor, or
– Any other reason the workers suspect an increased concentration, or
– A monitor alarm is triggered,
Then
– Leave the work area immediately and resume work only after monitoring confirms the hydrogen sulfide levels are stabilized to below 10 parts per million. Implement procedure requirements when re-entering.
4.5.4 Caution
5.1.4.1 At concentrations exceeding 10 ppm but below 20 ppm a one-time 10-minute entry is allowed. Enter with extreme care using a hand-held monitor. This applies only in a non-emergency situation with only slightly elevated concentrations.
5.1.4.2 At levels exceeding 20 ppm do not approach. The Owner or client personnel will monitor and advise when safe levels are reached.
4.6 Special Conditions/Confined Spaces
4.6.1 Entry into confined spaces such as tanks, pits, process vessels, and trenches shall be controlled by a permit system (see EHS Procedure 033).
4.6.2 Confined spaces that have contained hydrogen sulfide shall be inspected and tested for oxygen deficiency, hydrogen sulfide, and other contaminants and shall be thoroughly ventilated, cleaned, neutralized or washed, and then re-tested for hydrogen sulfide and oxygen prior to and during entry.
4.6.3 Possible buildup of hydrogen sulfide into the confined space while work is in progress shall be prevented by positive means such as forced air ventilation.
4.6.4 Employees entering confined spaces where they may possibly be exposed to hydrogen sulfide shall adhere to the following:
4.6.4.1 Type C supplied-air respirator operated in the continuous flow or pressure-demand mode and an auxiliary self-contained breathing air supply: or
4.6.4.2 Self-contained breathing apparatus operated in the pressure demand mode equipped with a full facepiece.
4.6.4.3 Each employee entering the confined space shall wear a suitable harness with lifelines tended by another employee outside the space who also shall be equipped with the necessary protective equipment, including a self-contained breathing apparatus that operates in the pressure demand mode and has a full facepiece.
4.6.4.4 Communications (visual, voice, signal line, telephone, radio, or other suitable means) shall be maintained by the standby person with the employee inside the enclosed space.
4.6.4.5 All employees involved shall be trained on hydrogen sulfide, confined space, and respiratory protection prior to job assignment.
4.7 Hydrogen Sulfide Hazard Information
4.7.1 Recognition
Hydrogen sulfide is a colorless poisonous gas, which is heavier than air. It is detectable by its rotten egg smell at very low concentrations of less than 1 part per million. Concentrations of hydrogen sulfide higher than 20 parts per million deaden the sense of smell. This can happen very rapidly and at high concentrations, the ability to smell the gas can be lost instantaneously. DO NOT rely on your sense of smell to indicate the continuing presence of hydrogen sulfide or to warn of hazardous concentrations.
4.7.2 Where does it come from?
Hydrogen sulfite occurs naturally in crude petroleum, natural gas, and hot springs. It is produced by bacterial breakdown of organic materials and human and animal wastes (sewage). Industrial activities that can produce the gas include petroleum/natural gas drilling and refining, wastewater treatment, coke ovens, tanneries, and kraft paper mills. Hydrogen sulfide can also exist as a liquid compressed gas.
4.7.3 Hazardous properties
Hydrogen sulfide is heavier than air and may travel along the ground. It collects in low-lying and enclosed, poorly ventilated areas such as basements, manholes, sewer lines, underground telephone vaults, and manure pits.
For work within confined spaces, use appropriate procedures for identifying hazards, monitoring, and entering confined spaces.
Hydrogen sulfide is a highly flammable gas and gas/air mixtures can be explosive. It may travel back to the sources of ignition and flashback. If ignited, the gas burns to produce toxic vapors and gases, such as sulfur dioxide.
4.7.4 Review of health effects
4.7.4.1 Low concentrations of Hydrogen Sulfide irritate the eyes, nose, throat, and respiratory system (e.g., burning/tearing of eyes, cough, shortness of breath). Asthmatics may experience breathing difficulties. The effects can be delayed for several hours, or sometimes several days when working in low-level concentrations. Repeated or prolonged exposures may cause eye inflammation, headache, fatigue, irritability, insomnia, digestive disturbances, and weight loss.
4.7.4.2 Moderate concentrations can cause more severe eye and respiratory irritation (including coughing, difficulty breathing, accumulation of fluid in the lungs), headache, dizziness, nausea, vomiting, staggering, and excitability.
4.7.4.3 High concentrations can cause shock, convulsions, inability to breathe, extremely rapid unconsciousness, coma, and death. Effects can occur within a few breaths, and possibly a single breath.
4.7.5 Exposure
The primary route of exposure is inhalation and the gas is rapidly absorbed by the lungs. Absorption through the skin is minimal. People can smell the “rotten egg” odor of hydrogen sulfide at low concentrations in air. However, with continuous low-level exposure, or at high concentrations, a person loses his/her ability to smell the gas even though it is still present (olfactory fatigue). This can happen very rapidly and at high concentrations, the ability to smell the gas can be lost instantaneously. There DO NOT rely on your sense of smell to indicate the continuing presence of hydrogen sulfide to warn of hazardous concentrations.
Contact with liquid hydrogen sulfide causes frostbite. If clothing becomes wet with the liquid, avoid ignition sources, remove the clothing, and isolate it in a safe area to allow the liquid to evaporate.
4.7.6 Protection/ rescue
4.7.6.1 Before entering areas where hydrogen sulfide may be present, air must be tested for the presence and concentration of hydrogen sulfide by a qualified person using air monitoring equipment, such as hydrogen sulfide detector tubes or multi-gas meter that detects the gas.
4.7.6.2 If the gas is present, space/area must be ventilated continually to remove the gas.
4.7.6.3 If the gas cannot be removed, the person entering the space/area must use appropriate respiratory protection and any other necessary personal protective equipment, rescue, and communication equipment.
4.7.6.4 A level of Hydrogen Sulfide gas at or above 100 ppm is considered to be Immediately Dangerous to Life and Health (IDLH). Entry into IDLH atmospheres can only be made using:
4.7.6.4.1 A full facepiece pressure-demand self-contained breathing apparatus (SCBA) with a minimum service life of thirty minutes, OR
4.7.6.4.2 A combination of full facepiece pressure-demand supplied-air respirator with an auxiliary self-contained air supply.
4.7.6.5 If the Hydrogen Sulfide levels are below 100 ppm, a full facepiece air-purifying respirator may be used with the appropriate filter cartridge/canister for hydrogen sulfide.