Hydrogen sulfide fumes from a 12-foot-deep sewer line killed four workers on Nov. 1 at the Lakehead Blacktop Demolition Landfill in Superior, Wis. The level of deadly gas at the bottom of the 3-foot-diameter manhole was so high that it would have immediately knocked them unconscious, according to experts at the scene.
Paul E. Cossalter, 41, died along with brothers Joseph P. Kimmes III, 44, and Scott A. Kimmes, 40, and Harold Tim Olson, 47. After the first man entered the manhole and collapsed, the others followed as each one saw the previous rescuer succumb. Two other workers at the privately owned landfill called 911 after the men failed to emerge.
Firefighters with breathing apparatus recovered the bodies as workers pumped out water to help. Since hydrogen sulfide is slightly heavier than air, it stayed below ground and didn’t threaten the helpers. The deceased were not wearing respirators or safety masks, according to firefighters.
The workers were installing a new pump in a large collection tank that held drainage and leeched water from the landfill. The water is eventually pumped into the city sewer system. The landfill holds demolition products, such as razed buildings, and contains no garbage or hazardous materials, according to Joseph Kimmes II, father of the Kimmes brothers and founder of J. Kimmes Construction, which owns the landfill and several other area companies.
Lethal fumes
The fatalities provide a lesson in the necessity of confined-space safety, as 60 percent of confined-space fatalities are would-be rescuers, many untrained and ill-equipped.
Hydrogen sulfide is poisonous, highly flammable, explosive, and colorless. Levels of 150 parts per million (ppm) or greater cause the olfactory nerve to lose sensitivity. The first time a person breathes the gas, the nose can detect a rotten egg odor, but on the second or third inhalation, the person can no longer smell it.
At 600 ppm, breathing is inhibited as the gas fills the lungs and causes unconsciousness. The lungs of those exposed to 700 to 800 ppm or greater are paralyzed. These victims die quickly unless they are removed immediately from the gas area and given oxygen. However, many suffer brain damage, often permanent.
Those exposed to lower concentrations of the gas can experience eye irritation, a sore throat and cough, shortness of breath, and fluid in the lungs. These symptoms usually go away in a few weeks. Long-term, low- level exposure may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness.
The National Institute for Occupational Safety and Health (NIOSH) considers 300 ppm immediately dangerous to life or health and recommends a maximum, 10-minute exposure level of 10 ppm. OSHA sets an acceptable ceiling concentration of 20 ppm and a maximum of 50 ppm allowed for 10 minutes if no other measurable exposure occurs. Firefighters at the scene in Superior recorded a hydrogen sulfide reading of 200 ppm, according to Superior Fire Chief Tad Matheson.
Prevention and protection
The risk of exposure to toxic gases in confined spaces requires workers to take special precautions. OSHA regulations require sewer crews to measure the atmosphere in manholes with a gas detector before removing the lid, as agitating sewage can release hydrogen sulfide into the manhole chimney.
Workers entering manholes must be trained in confined-space entries; learn the proper use of harnesses, hoists, ladders, and ropes; and wear the appropriate personal protection equipment.
“The simple use of an air monitor gives employees a warning of the hydrogen sulfide prior to entry,” says Ed Fitzgerald, lead safety trainer for Jack Doheny Supplies in Twinsburg, Ohio. “The use of forced-air ventilation lowers the concentration of hydrogen sulfide to a permissible exposure level, and the use of a tripod-type rescue device prevents other employees from entering the confined space.”
For hydrogen sulfide levels up to 100 ppm, NIOSH recommends a powered, air-purifying respirator with cartridge, gas mask with chin-style front- or back-mounted canister, or self-contained breathing apparatus with full facepiece. A continuous gas monitoring device is a sensible addition to respiratory equipment.
“The use of only respiratory protective equipment is not the answer,” says Fitzgerald. “Training in hazardous material gives people the knowledge and understanding to handle toxic atmospheres.”
Training matters
Employers are responsible for establishing safety programs for their companies. “The ability to recognize when crews are in over their heads or beyond their training level is one of the most important things you can accomplish in your training sessions,” says Fitzgerald. “The use of monitoring, ventilation, and rescue equipment must be backed up by a company-written health and safety program.”
The lack of specific procedures to ensure safe entry into areas containing hazardous gases too frequently causes fatalities. Employers who implement carefully written and enforced procedures can help prevent potentially deadly accidents.
“If you take the time to build, maintain, and enforce a health and safety program, the productivity, professionalism, and attitude of your employees will increase to a level that every customer will notice and appreciate,” says Fitzgerald. “The ability to go home in good health at the end of the day is priceless.”
Visit www.osha.gov to review health and safety standards or to learn how to create a program using the standards as a step-by-step road map. Building a health and safety program takes time and employee involvement. According to Fitzgerald, the greatest mistake employers make is copying a program off the Internet without the ability or knowledge to follow through.
