Hydrogen Sulfide

[Music] [HYDROGEN SULFIDE H2S SAFETY] When working at sea, some hazards are obvious; others are not. They are invisible to the human eye and may not be detected by our other senses making them that much more dangerous. Whether you are working on a product tanker or moving crude oil, you need to be aware of the dangers that are related to your job. One of these dangers is hydrogen sulfide gas or H2S. If proper precautions are not taken, it can be lethal. In this video, we will review hydrogen sulfide and its hazardous properties, the common exposure limits and what they mean, how to prevent hazards through proper monitoring and protection; and lastly, the proper procedures in the event of exposure. [FIRST AID PROCEDURES] [HYDROGEN SULFIDE HAZARDS] Hydrogen sulfide is a naturally occurring chemical compound, that can be found in a variety of petroleum substances including crude, natural gas, diesel and bunker fuel. It is largely the result of bacterial breakdown of organic matter, industrial activities and petroleum refineries. At the molecular level, hydrogen sulfide is composed of two hydrogen atoms and one sulfur atom and is commonly referred to as H2S. It is a gas at room temperature, that may be cooled to a liquid and stored for transportation. In liquid state, hydrogen sulfide can measure at much lower concentrations when compared to the same quantity, when it gases off. In gas state, H2S is colorless, toxic, corrosive, flammable and heavier than air. It can combine with iron oxide or rust that is already present in a cargo tank, which then creates iron sulfide. At this point, if oxygen is introduced into the tank, the iron sulfide could ignite. Over time, hydrogen sulfide may also corrode metal pipes, which could lead to leakage and the possibility of exposure. Hydrogen sulfide is commonly referred to as the sewer gas due to the rotten egg smell associated with it. However, you can't always detect hydrogen sulfide with your nose. One misconception is that you would be able to smell it before there is a problem; and that’s not true. Your nose can't detect it at low enough levels. And even if it does because of old factory fatigue for hydrogen sulfide your nose loses its ability to smell the rotten egg smell. So, you think it's good, you think it's safe and you decide to go in anyway. And in the end you could be overcome. Hydrogen sulfide targets several parts of your body including your eyes, respiratory system and central nervous system. Contact with skin, though not as common, results in frostbite. The most likely and dangerous exposure pathway for H2S is through inhalation. When H2S enters our lungs, it is rapidly absorbed into the bloodstream. At very low levels, our bodies are able to oxidize or break down H2S into a harmless substance. When too much H2S is inhaled, the body cannot keep up and eventually becomes asphyxiated. The effects of hydrogen sulfide in your body primarily depend on the concentration and duration of exposure. But they may differ depending on your physiology and susceptibility. At low concentration of exposure, at around 0.01 to 0.5 parts per million, you may start to detect the minimal odor of rotten eggs. Between 1 to 10 parts per million, the odor will become more offensive and easily detectable. Prolonged exposure may start to cause watering of the eyes and mild headaches. Between 10 to 20 parts per million, irritation of the eyes and breathing passages increases. You may experience fatigue, loss of appetite, mild nausea and increased headaches. These symptoms will continue to worsen. And as the concentration passes 100 parts per million, it will lead to significant irritation of eyes and breathing passages causing coughing, headaches and nausea. Within a few minutes of exposure, your sense of smell will be lost along with your awareness of danger. Above 250 to 500 parts per million will cause difficulty breathing, fluid in lungs, vomiting, dizziness and loss of coordination. Between 500 to 750 parts per million will cause eye damage within 30 minutes, breathing stops and then rapid unconsciousness. If the victim is not rescued and resuscitated, death will result. Anything past 750 parts per million death is instant. [Eye damage within 30 min] [INSTANT DEATH] [EXPOSURE LIMITS] There are several standards for the evaluation of exposure limits to chemicals in a workplace. You need to know which standards your company uses. The common exposure limits for hydrogen sulfide are as follows: OSHA's permissible exposure limit or PEL is set at 10 parts per million for an 8-hour time weighted average or TWA. This is the average exposure allowed for an 8-hour workday. This cannot exceed 15 parts per million for its 15-minute short-term exposure limit or STEL. Keep in mind that OSHA's permissible exposure limit is enforced by law. The ACGIH sets standards for the threshold limit values or TLV at 1 part per million for the 8-hour time weighted average; and 5 parts per million for the 15 minutes short-term exposure limit. And this is significantly lower than OSHA's permissible exposure limit. NIOSH sets the limit for the recommended exposure level or REL at 10 parts per million ceiling for 10 minutes. NIOSH also sets the exposure level of immediately dangerous to life and health or IDLH to 100 parts per million. Anything above that is considered immediately dangerous to life and health. And once you start to get up two levels of about 700 PPM that could technically mean instantaneous death. [MONITORING & PROTECTION] Your company should have a safety awareness program in place when dealing with H2S. This may include an H2S awareness and training plan, a permit to work system, a job safety analysis meaning prior to starting work, an H2S detection system, emergency evacuation and emergency procedures, and personal protective equipment. Preventing exposure is always the key to a safe work environment. Engineering controls like the vapor recovery system are there to recover the vapors for processing or for burning them at dedicated facilities. Most of the processes on board are performed in a close system. However, there is always the potential for exposure when the system is open such as maintenance operations, equipment leakage and carryover losses. Crewmen on board may also become exposed during routine operations such as cargo transfers, tank gauging and sampling, tank venting, tank cleaning and bunkering. Because H2S is heavier than air, the gas may accumulate in low-lying or poorly ventilated areas such as tanks and confined spaces. Ventilate the space continually if it is safe to do so. Make sure the work area around you and the atmosphere you are about to enter is monitored correctly. There are many tools to monitor your workplace such as detector tubes or personal electronic monitors. Electronic alarms which continuously monitor H2S concentrations may be installed near cargo tanks or vents. Always wear a personal gas detector. If there is an alarm, you will have both an audible and visible signal, it will flash and beep; and many of the new ones also vibrate. If the alarm starts, leave the area immediately. Always calibrate your equipment prior to each day's use with the calibration gas provided by the manufacturer of your equipment, okay? Then many of the 4-gas monitors will have remote sampling probes that'll allow you sample without going into the space; and you are going to always want to sample the top and the middle and the bottom in case there's stratification of the different gases. If you must enter a space where hydrogen sulfide is present, you are required to use appropriate respiratory protection and any other necessary personal protective equipment. For IDLH levels of 100 parts per million or above, you are required to wear a full-face self-contained breathing apparatus, SCBA or a full-face supplied air respirator. Below 100 parts per million, a cartridge-type half-mask air-purifying respirator may be utilized depending on its assigned protection factor and after considering the maximum use concentrations in your workplace. Since H2S has the potential to cause eye irritation, goggles or a full-face respirator may be needed at concentrations well below 100 parts per million. Refer to your company's procedures on the types of respiratory protection that you must use. You should be trained in donning your breathing apparatus and fit testing your equipment properly. Consult your company's SMS or manufacturer's instructions to determine if you are using your equipment correctly. If you are unsure of proper PPE use or you see work being performed unsafely, stop work immediately to prevent injury. Use a risk assessment or job hazard analysis to determine the safe way to complete the job. [FIRST AID PROCEDURES] If you suspect the presence of H2S in the atmosphere or in case of an alarm or emergency, leave the area, get to a safe zone and get fresh air. If someone has collapsed from breathing H2S, do not attempt to rescue them without donning the proper breathing apparatus and proper safety equipment; if you do not, you may become a victim as well. In many cases, over 50% of the cases, the would-be rescuers are also part of the fatalities. So, over 50% of the fatalities in confined spaces are to the would-be rescuers. If a person breathes in large amounts of H2S, move the exposed person to fresh air as soon as possible. If breathing has stopped and you are trained, perform artificial resuscitation; get fresh air into their lungs and oxygen into the bloodstream immediately. Contact emergency medical responders as soon as possible. In a case of severe eye irritation, get to a safe zone, remove any corrective lenses and rinse eyes with large amounts of water for at least 15 minutes then seek medical attention. Proper training including knowing the proper protective equipment and the proper procedures will help you to prepare for any emergency. In this video we’ve learned what hydrogen sulfide is and its hazardous properties, the common exposure limits and what they mean, how to prevent hazards through proper monitoring and protection; and lastly, the proper procedures in the event of exposure. Even though you are an employer or a company is required to monitor your workplace and provide engineering and administrative controls. You need to know what dangers you may face and how to protect yourself. With the proper protective equipment, reinforced training and a good understanding of possible dangers you can avoid tragic consequences.