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H2S: That Rotten Egg Smell Is Life Threatening  Almost
everyone has experienced that unpleasant rotten egg smell that comes from
Hydrogen Sulfide (H2S) gas, but it is generally not a serious
health problem when we’re traveling briefly near a dairy, poultry
farm or wastewater treatment plant. The exposure level is low and short,
but it should never be ignored because it can be fatal.The same cannot always be said about H2S gas accidents within the workplace. Exposure to high levels of H2S gas for even a brief time can be fatal. And most people don’t realize that H2S is also combustible, capable of causing major explosions and fires. H2S is never to be under-estimated in its potential for harm in the workplace. Understanding H2S Gas Hydrogen sulfide is produced naturally by decaying organic matter and is released from sewage sludge, liquid manure, sulfur hot springs, and natural gas. It is a by-product of many industrial processes, including: petroleum refining, tanning, mining, wood-pulp processing, rayon manufacturing, sugar-beet processing, and hot-asphalt paving. Hydrogen sulfide is used to produce elemental sulfur, sulfuric acid, and heavy water for nuclear reactors. It is a colorless, flammable, highly toxic gas. It is shipped as a liquefied, compressed gas. It has a very noticeable rotten-egg odor. Inhalation is the major route of hydrogen sulfide exposure. Standards and Guidelines Various agencies of the US government have set the following standards for H2S exposure:  OSHA ceiling = 20 ppm OSHA maximum peak = 50
ppm (10 minutes, once, no other exposure) NIOSH IDLH (immediately
dangerous to life or health) = 100 ppm AIHA ERPG-2 (emergency
response planning guideline) (maximum airborne concentration below which
it is believed that nearly all individuals could be exposed for up to 1
hour without experiencing or developing irreversible or other serious health
effects or symptoms which could impair an individual's ability to take protective
action) = 30 ppm.Exposure Symptoms According to the U.S. government’s Agency for Toxic Substances & Disease Registry, H2S gas is rapidly absorbed in the lungs. Hydrogen sulfide is slightly heavier than air and may accumulate in enclosed, poorly ventilated, and low-lying areas. The odor threshold (0.5 ppb) is much lower than the OSHA ceiling (20 ppm). Although its strong odor is readily identified, olfactory fatigue occurs at high concentrations and at continuous low concentrations. For this reason, odor is not a reliable indicator of hydrogen sulfide's presence and may not provide adequate warning of hazardous concentrations. H2S is a mucous membrane and respiratory tract irritant; pulmonary edema, which may be immediate or delayed, can occur after exposure to high concentrations. Symptoms of acute exposure include nausea, headaches, delirium, disturbed equilibrium, tremors, convulsions, and skin and eye irritation. Persons exposed to hydrogen sulfide pose no serious risks of secondary contamination to personnel outside the Hot Zone. Preventing H2S Gas Accidents For over 40 years, General Monitors has been a leader in the detection of H2S gas and prevention of industrial accidents. The company’s first breakthrough in thin film metal oxide semiconductor (MOS) technology for H2S gas sensors set the industry standard for detection in the 1960s. These highly reliable devices continue to provide protection today in many industries. During the late 1990s, General Monitors began new work in electrochemical sensors that eventually led to more breakthroughs in both fixed and portable detectors for H2S gas. The company’s latest electrochemical cells for H2S detection for the Models TS4000 and TS400 now offer superior protection. The TS4000 and the TS400 both sense H2S over a broad range from 0 to 100 ppm. The advanced electrochemical cell for these models, manufactured by General Monitors, features a precision laser weld design that provides superior casing integrity. This rugged construction prevents separation and leaking, which are common problems in other electrochemical sensor designs, to ensure superior performance. The cells operate over a broad temperature range from -40 to +50°C. TS4000 Intelligent Toxic Gas Detector The TS4000 Toxic Gas Detector relies on a sophisticated electrochemical cell sensor to detect H2S and many other toxic gases. Its design offers numerous advanced features, including long distance remote mounting up to 2,000 feet, dual redundant MODBUS communications, 8 amp relays, three-digit display, 4-20mA output, and indication of remaining sensor life. All of the TS4000’s electronics are contained within an explosion-proof housing so that sensor information can be processed at the sensor site. Additionally, the interface module’s galvanically isolated, intrinsically safe design supports sensor field replacement without special tools or hot work permits. Easy to install -- the TS4000 features one-person calibration and can virtually self-calibrate by activating a magnetic switch and applying gas. Process engineers who need to protect people and equipment will find that the TS4000 is ideal for chemical, oil/gas, wastewater and other hazardous environments. Additional applications include public utilities, refineries, pharmaceuticals and food and beverage. Click here for more information on the TS4000 Toxic Gas Detector. TS400 Toxic Gas Detector The compact TS400 Gas Detector (1.75-x-4.5 in.) fits within the palm of your hand. It weighs only 8 ounces, and its smaller size allows fixed placement in crowded plant conditions where other larger fixed gas detectors won’t fit. With one-person, adjustment-free calibration, this detector is easy to install and reduces maintenance costs over the life of the device. The TS400 is a two-wire loop-powered H2S detector that eliminates the need for an output loop supply, which reduces installation and cabling costs. Its electronics are encapsulated within a chemically resistant plastic housing with detector information processed at the point of detection. A built-in LCD indicator also provides local status, fault and calibration cues. This device can be used in general purpose, intrinsically safe, increased safety or explosion-proof areas when used with specified TS400 accessories. Click here for more information on the TS400 Toxic Gas Detector. Copyright © 2005 General Monitors, Inc. All logos, brand and product names are registered trademarks of their perspective owners. All rights reserved. Questions or comments to ToxicGas@generalmonitors.com |
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