Transcript
The 1 ppm Hydrogen Sulfide Threshold: Are you prepared?
ST-13295-2007
Dräger recently worked together with the American Society of Safety Engineers (ASSE) to conduct a survey of its members to determine their awareness of the new hydrogen sulfide standard and the preparedness of their organizations to meet this threshold. This document summarizes the results of the survey.
Among deaths from gas inhalation in the workplace, hydrogen sulfide (H2S) remains the leading cause1. Commonly known as sewer gas, sour gas and stink damp, hydrogen sulfide goes by a number of names, including dihydrogen sulfide, sulphur hydride, hydrosulphuric acid, sulfuretted hydrogen, and hepatic gas. Regardless of what you call it, it can be lethal: any inhalation of H2S in a sufficiently high concentration can cause death. RECOMMENDED DETECTION THRESHOLDS ARE BEING LOWERED
Industrial hygiene organizations are recommending lower thresholds for detection of hazardous gases. For example, the American Conference of Governmental Industrial Hygienists (ACGIH) recently put into place the following limits for H2S: –– Threshold Limit Value (TLV): 1 ppm –– Time Weighted Average (TWA): 1.4 mg/m3 –– Short Term Exposure Level (STEL): 5 ppm, 7.0 mg/m3 At this point these are guidelines, not legal requirements.
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http://cupe.ca/health-and-safety/Hydrogen_Sulfide
LACK OF INDUSTRY AWARENESS
The study reveals that 53 % of safety experts in the oil and gas industry are un-aware of the new standards. SHORT TERM IMPACT ON HYGIENE PRACTICES
The majority (76 %) of safety experts who know about the new standards reported no urgency to adopt them, despite the increased safety that can result. When asked why they chose not to take action in the short term, their responses were highly varied. –– 33 % did not make a change because it was a recommendation rather than a regulatory standard –– 26 % felt that the data does not accurately support the need to lower the threshold limit –– 11 % said they use alternative Personal Protective Equipment to protect their workers –– 10 % said their current Standard Operating Procedures (SOP) do not allow for this change to occur –– Other responses included “still evaluating,” “not relevant to the business,” “not feasible to incorporate,” “evaluating equipment that can reliably measure to 1 ppm”
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H2S SURVEY | AMERICAN SOCIETY OF SAFETY ENGINEERS
CURRENT ALARM LEVELS VARY
MAJORITY THINK NEW STANDARDS
GREATLY
WOULD INCREASE COSTS
So if companies are not using the new TLV standard of 1ppm, what H2S alarm level are they currently using? The responses varied greatly: –– 39 % use 10 ppm and 15 ppm –– 35 % use 5 ppm and 10 ppm –– 15 % use 10 ppm and 20 ppm
The majority (70 %) of responders think that adopting the 1 ppm levels in their workplace would affect worker-protection costs.
FEW HAVE MADE ADJUSTMENTS RECENTLY, FEW PLAN TO DO SO
Of those companies who have not adopted the new ACGIH guidance, only 24 % have adjusted their H2S limits within the last three years. Moreover, only 34 % anticipate adjusting their current H2S limits in the near future. MOST BELIEVE DETECTION BELOW 1 PPM IS IMPORTANT, BUT FEW THINK EXISTING INSTRUMENTS CAN DO IT
Most safety engineers surveyed (64 %) believe that it is important that instruments can detect below 1 ppm. However, only 41 % believe that a 1 ppm H2S resolution can be seen with accuracy in personal monitoring instruments and 74 % are concerned that with the 1 ppm resolution there will be an increase in false readings.
a central device for review at a later time. 56 % do not allow it under any circumstance, and 9 % allow it only with approval of senior management. KNOWLEDGE OF USING PENTANE
ALMOST ALL USE PERSONAL
AND METHANE
MONITORING INSTRUMENTS
62 % of these companies require a daily bump test. Most of those who don’t require a daily bump test have other requirements, such as daily or weekly testing.
When survey participants were asked if they were aware of the concerns with using pentane as the only gas source for calibration of catalytic sensors in gas monitoring instruments a little more than half (53 %) were unaware of the concerns or that this practice is recommended. 47 % were aware that methane should be used for periodic testing as well.
BUMP TESTING AND CALIBRATIONS
SUMMARY OF FREE FORM RESPONSES
For bump tests and calibrations: –– 55 % use an internal electronic/ mechanical docking station to complete checks and record results –– 31 % manually calibrate the instruments via direct flow of calibration gas and record the results –– 14 % use a third party to conduct calibrations and a manual application of gas for bump tests
The most common responses are grouped below. –– “It’s overkill”: A TWA of 8 hours at 1 ppm is hard to monitor and enforce. Standard practice in upstream oil and gas has monitors set at 10 ppm with the emergency response plan to evacuate immediately to a safe muster point. The STEL is more realistic; an alarm set at 5 ppm with evacuating the location is better –– “Will require coordination”: Implementation requires coordination with customers because potential exposures can occur at their sites
92 % of those companies surveyed use personal monitoring instruments as a part of their Industrial Hygiene program.
Only 18 % allow third-party devices to collect and transmit industrial hygiene data from calibration and bump test stations on their corporate networks to
H2S SURVEY | AMERICAN SOCIETY OF SAFETY ENGINEERS
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–– Recommendation not intended for healthy workers: The ACGIH Committee that established the revised TLV based their 1 ppm level on the premise that 15 % of the US adult working population has asthma and have negative reactions to H2S at 1 ppm. It was never the committee’s intent to change the standards for healthy workers –– Unrealistic: Ambient H2S concentrations in oilfields are frequently found at 3 – 5 ppm, so a move to 1 and 5 ppm levels is unrealistic for oil & gas. Normal ranges in sour gas facilities usually range between 1 to 3 ppm levels
–– Won’t be adopted because it’s not the law: while safety professionals generally want a more stringent standard, it won’t be adopted because of direct or indirect costs and the belief that tougher standards will be cumbersome and lead to poor audit pass rates –– Current standard shows no harm to workers: for decades, oil fields have operated using 10 ppm as the PEL/TLV with no quantifiable effect on workers –– Shorter sensor lifespan: H2S gas used in calibration of multigas meters shortens the life span of the LEL sensor
–– Not physically possible: current equipment is not yet consistent on 1 ppm resolution –– Not based on industry knowledge: the committee made these recommendations without adequate H2S knowledge or work history
SUMMARY
by considering steps that support these lower limits before they become mandatory. The potential benefits – both in terms of worker safety and cost savings – are significant.
Dräger is an international leader in the fields of medical and safety technology. Our products protect, support and save lives. Please visit www.draeger.com for more information.
In summary, while the new H2S limits are recommendations and carry no legal obligations at this time, the message is clear. There is a strong belief by agencies such as ACGIH that these exposure levels will create a safer work environment. Therefore, it is likely that there will be a wider acceptance and implementation among industrial hygienists as more data becomes available. Forward-thinking companies will be preparing for evolution of these standards
Dräger wishes to thank the membership of the ASSE for their participation in this survey. We hope this summary provides a useful perspective on the current perspective of ASSE members regarding the lower hydrogen sulfide threshold.
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