CSB Safety Video: Hazards of Nitrogen Asphyxiation

workers who have survived uh these episodes describe a funny feeling where they can take a deep breath and yet they still feel like they're suffocating on November 5th 2005 two workers died at the Valero Energy Corporation refinery in Delaware City Delaware they had entered a reactor vessel a confined space that was filled with nitrogen and odorless invisible gas the accident occurred during a maintenance operation at the 5,000 acre facility which processes 180,000 barrels of crude oil per day the complex is one of Valero's 18 us refineries and has 570 employees the US chemical safety board

investigated the accident and issued a case study with safety recommendations this is not a new issue for the csb in fact the board conducted an earlier investigation into the hazards of nitrogen asphixiation and is Ed a safety bulletin in 2003 the bulletin identified 85 nitrogen asphixiation incidents that occurred between 1992 and 2002 killing 80 people and injuring 50 that study and incidents since it was issued in 2003 show that lives continue to be lost because workers are not being made aware of the dangers of oxygen deprivation oxygen comprises 21% of the the air we breathe

and humans cannot survive for long when it drops below about 19% in refineries and chemical plants dangerous low oxygen environments are created when inert gases like nitrogen are used to remove oxygen from pipes and Equipment the risk of an oxygen deprived atmosphere is that you'll get trapped in that situation you'll get trapped and die Dr T Gadi is a physician and shares the Department of Environmental and occupational health at the George Washington University he describes the effects of oxygen deprivation on workers from the moment a person first goes in to an oxygen deprived atmosphere they

are effectively impaired and when the oxygen deprived atmosphere begins to enter the lungs the oxygen in the blood that's going to the brain starts to fall that affects the brain's judgment it affects coordination it affects the ability to exert strength they fall down fall unconscious or they're judgement is so impaired that they can't find their way back out and they die the csb case study on the Valero accident underscores the importance of strict safeguards when working around low oxygen environments workers are in danger not only inside confined spaces but also around openings where inert gases

like nitrogen are flowing out here's what we believe happened the night of the accident fero's hydrocracker reactor number R1 was shut down for maintenance a large pipe elbow had been removed creating an opening surrounded by large steel bolts in the middle of the platform workers had wrapped red tape around the bolts and covered the opening with plywood in plastic nitrogen flowed into the reactor and exited from the covered opening nitrogen is invisible but it is colored light green here for illustration workers had attached a sign reading danger confined space do not enter without permit however

there were no specific warnings posted about the nitrogen Hazard a crew of Matrix contract workers had received a Valero issued permit to reinstall the pipe elbow the safe workk permit did not warn the crew that the reactor was filled with nitrogen in fact the permit stated quote nitrogen Purge in not applicable two contract workers removed the plywood cover and cleaned the ledge around the opening at about that time a third worker noticed a roll of duct tape lying 5 ft down inside the reactor this presented the crew with a problem the tape would cause the

reactor to fail Valero's cleanliness inspection and they would not be allowed to reinstall the elbow until it was removed however entering the reactor to remove the tape would require obtaining a specially trained and equip crew and a confined space entry permit from Valero that process would take many hours and delay the installation of the elbow which was to be completed before the end of the night shift now half over in addition the crane needed for lifting the 5ton elbow into place had just become available for a short period to avoid the long delay one worker

stood near the opening with a long flexible wire and made several attempts to hook the tape but he was unsuccessful what seemed like an easy task just wasn't working most likely the worker then got closer by sitting on the ledge of the opening with his legs dangling inside but he still could not remove the tape based on the evidence the csb developed two possible scenarios for what happened next in the first scenario the worker lowered himself into the reactor to quickly grab the tape relying on his Foreman nearby to insert a ladder so he could

climb back out but after lowering himself into the reactor he inhaled the nearly pure nitrogen inside deprived of oxygen he quickly collapsed in the second scenario the worker on the ledge leaned over the opening trying to get closer to the tape at that point he either accidentally slipped into the reactor or he breathed in the oxygen deficient atmosphere just above the opening lost Consciousness and slid in what happened next added to the tragedy an eyewitness saw the foreman and the contract administrator peering into the reactor the stricken worker was lying unconscious inside the foreman quickly

inserted the ladder into the reactor and climbed down to help his fellow worker but without a breathing apparatus he too collapsed from the lack of oxygen the contract administrator declared an emergency on his radio Valero operators then sounded the unit alarm when company emergency responders arrived a short time later they saw both victims lying motionless inside the reactor a handheld meter inserted through the opening showed less than 1% oxygen a lethal atmosphere wearing supplied air breathing equipment the responders entered the reactor a rescue hoist was used to remove the workers it was now almost 10

minutes since the first worker had collapsed attempts to revive the men were unsuccessful and both were later pronounced dead at the hospital the csb believes that two workers died within a few minutes of entering the nitrogen filled reactor this tragic accident was avoidable the csb determined that company training programs and Industry good practice guidelines do not adequately warn workers of the dangers of oxygen deficient atmospheres inside confined spaces this video shows the inside of the Valero reactor where the accident occurred the roll of tape still visible just 5 ft below the opening it's a situation

where a worker might be tempted to believe he could quickly get in and out to accomplish what appeared to be a simple task but safety experts warn that would be fatal it is far too dangerous for any worker to try to duck in and duck out holding their breath you can't hold your breath long enough or reliably enough to do this nitrogen gas hazards are not limited to the inside of confined spaces the csb concluded that industry safety guidelines Valero procedures and OSHA standards do not adequately warn of low oxygen hazards outside of confined spaces

near openings a person who's leaning over for example with their face close to an opening in a a vessel with nitrogen under pressure is not going to be breathing the regular concentration of oxygen in air that can impair judgment and it can also cause the person to pass out warning signs and barricades are additional protection for workers tempted to enter low oxygen environments the CSP found that there was a confined space warning sign posted at the opening of the Valero reactor but it was only after the accident that the company put up a barricade around

the work area with a sign reading danger nitrogen and nert gas Purge in progress oxygen deficient atmosphere do not pass this point without author authorization when a worker does enter an oxygen deficient confined space and is overcome it can set the stage for further tragedy as other co-workers attempt rescue without proper breathing and rescue equipment this can lead to multiple deaths it's particularly sad because when an incident like this happens and you have a man down uh other workers invariably feel a very human urge to rescue the coworker so they they run into the situation

very often without getting self-contained breathing apparatus without getting an air supply and fall victims themselves it's not a question of the worker's judgment it's a question of the worker's training because if the worker has been adequately drilled and has been um informed of the proper procedures and these procedures have been enforced that should never happen following our investigation the CSP issued several safety recommendations to the Valero Delaware City refinery to the corporation to the maintenance contractor and to trade and safety organizations the recommendations emphasize the need for training in work around confined spaces and on

the dangers of oxygen deprivation the CSP recommended that the American petroleum Institute the oil industry's leading trade Association revise its guidelines for safe work in inert confined spaces the CSP recommends that the following critical information be conveyed to workers nitrogen rapidly overcomes the victim there is no warning before being overcome oxygen deficiencies may exist just outside a confined space opening any personel attempting rescue must strictly follow confined space entry procedures to avoid further loss of life and use warning signs and barricades where appropriate nitrogen and other enered gases are widely used and vital components in

the operation of chemical plants and oil refineries but they can be silent killers in confined spaces the csb believes that lives will be saved if companies provide comprehensive training and strict enforcement of safe work procedures to view the written csb case study on Valero and the csb nitrogen safety bulletin please visit our website at csb.gov thank you for watching the csb safety video