Chemical related incidents come in all sizes and locations. It is not just accidents at chemical manufacturing facilities or transportation centers that can result in emergency services responding to chemical incidents. This was seen last week in a chemical response incident in a small town in Pennsylvania last week. See the news story here, here, and here.
Residents in a residential area complained about the smell of chlorine (most familiar to people as the smell of bleach). Emergency responders located the source of the leaking chlorine gas, a cylinder inspecting and refurbishing shop located in an older residential area. The tank was sealed and the building ventilated. Local residents were told to shelter in place until the chlorine gas dissipated.
Four people were taken to the hospital ‘for observation’ according to news reports. It is not clear if they were employees at the company (most likely to have significant exposure) or nearby residents. There are no follow-up news reports so they were probably released after their observation period was completed with minimal complications.
Chlorine is typically shipped as a liquid in pressurized cylinders. When that pressure is released the liquid evaporates into a gas that forms a heavy, yellow-green vapor cloud. Chlorine is a toxic inhalation hazard (TIH) chemical that has been successfully used as a chemical weapon in WW I. The allowable exposure limit (OSHA PEL) is 1 ppm. It is detectable by its characteristic odor by most people at 0.32 ppm. The concentration of most concern is the immediately dangerous to life and health (IDLH) which is 1000 ppm. According to NIOSH exposure between the PEL and IDLG may lead to the following symptoms:
Burning of eyes, nose, mouth; lacrimation (discharge of tears), rhinorrhea (discharge of thin nasal mucus); cough, choking, substernal (occurring beneath the sternum) pain; nausea, vomiting; headache, dizziness; syncope; pulmonary edema; pneumonitis; hypoxemia (reduced O2 in the blood); and dermatitis.
People with other existing respiratory problems will exhibit symptoms at lower exposure levels than more healthy people.
The company has been in operation since 1946 (probably in the same location). They take DOT rated cylinders used for the transport of hazardous gasses and liquids and conduct the periodic safety inspections that PHMSA requires for such cylinders. The testing requires that the tanks be emptied, visually inspected and then filled with water. The tanks are then pressurized and observed for signs of leaks and the expansion of the tank is measured. The tanks that pass are then marked and recertified for hazmat service in accordance with PHMSA regulations.
The company’s web site would seem to indicate that the majority of the tanks tested at the site were propane tanks. The web site does indicate that other types of tanks are also tested, including ‘low pressure’ (<900 amounts="" and="" are="" areas="" at="" chlorine="" disinfection.="" for="" o:p="" of="" other="" parks="" plants="" psi="" relatively="" small="" tanks.="" tanks="" that="" these="" treatment="" types="" typically="" use="" used="" usually="" water="">900>
The web site indicates that there is a service fee for emptying propane tanks. There is no such fee listed for emptying chlorine cylinders so it would appear that the company required those tanks to be delivered empty. This would not be unusual for a small shop that did not handle chlorine for other reasons.
What May Have Happened
Unless the investigation by various government agencies (principally state EPA and OSHA) reveals unsafe practices that result in fines, the public will probably never hear the details of what happened at this facility. Based upon news reports, I can come up with a reasonable scenario for what might have happened.
The operator opening the cylinder would have been wearing minimal personal protective equipment (hopefully a half-face cartridge respirator, chemical goggles, a chemical jacket and industrial rubber gloves), expecting the cylinder to be empty. When the tank began to off-gas a significant amount of chlorine the operator would have been instructed to sound the local alarm and evacuate the immediate area.
Since the facility did not apparently expect to actually handle chlorine gas on site, there would probably not be ventilation systems in place to scrub the chlorine from the local atmosphere. Ideally the facility employees would move to an assembly area upwind of the facility and the local fire department would be notified. A properly equipped Hazmat Team would respond, seal the tank, ventilate the area, and conduct atmospheric testing until the area was cleared.
From the news reports it does not seem that the notification of the local emergency responders was made by the facility. This may have been due to confusion on the site, or it may indicate that smaller chlorine releases were normal enough that there was not an apparent need to report this incident.
If the facility were routinely handling cylinders with significant residues of liquid chlorine in the cylinders, I would expect the facility to have a lot more complex system in place for opening those cylinders including a local ventilation system equipped to scrub the chlorine gas from the atmosphere in the event of a release. I would define ‘significant residues’ as any visible liquid, but the EPA only requires reporting of spills over 10 lbs, so arguments could be made for any quantity between those limits.
Chlorine is a widely used hazardous chemical. As such, urban and suburban fire departments should have at least minimal training in handling chlorine related incidents. While the incidents of most concern will normally be found at manufacturing facilities and along transportation (chlorine is routinely shipped by rail and truck) routes, smaller incidents are not unusual.
It certainly appears from the news reports that the responders in this case knew what they were doing and responded effectively.