Once again I go to the well that just keeps on giving guidance… the International Fire Code (IFC). And again I do this as OSHA nor EPA have any standards for Chlorine when the amount is below the 1,500 pounds for OSHA’s PSM standard to apply. Of course, there is EPA’s RMP General Duty Clause, but this provides us with zero help in establishing the minimum design and operational standards. The IFC establishes a nice set of minimum requirements we can apply to our chlorine storage/handling/processing. But to be fair, we must first establish Chlorine as either a “Highly Toxic” or a “Toxic” hazardous material. This is needed because the IFC has different requirements based on the level of toxicity a HAZMAT may present. Very early in my career, I was introduced to Chlorine and Bromine and both organizations managed these materials as “Highly Toxic”; however, both of the organizations were world-class in the engineering of their chemical processes (PSM or not!). So the question is… where does Chlorine fall on the scale of toxicity?
Let’s first look at the IFC’s definitions of Highly Toxic and Toxic, which are simply based on the HAZMAT’s LD50 or LC50 levels:
(emphasis added by me)
HIGHLY TOXIC. A material which produces a lethal dose or lethal concentration which falls within any of the following categories:
1. A chemical that has a median lethal dose (LD50) of 50 milligrams or less per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each.
2. A chemical that has a median lethal dose (LD50) of 200 milligrams or less per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between 2 and 3 kilograms each.
3. A chemical that has a median lethal concentration (LC50) in air of 200 parts per million by volume or less of gas or vapor, or 2 milligrams per liter or less of mist, fume or dust, when administered by continuous inhalation for one hour (or less if death occurs within 1 hour) to albino rats weighing between 200 and 300 grams each.
Mixtures of these materials with ordinary materials, such as water, might not warrant classification as highly toxic. While this system is basically simple in application, any hazard evaluation that is required for the precise categorization of this type of material shall be performed by experienced, technically competent persons.
TOXIC. A chemical falling within any of the following categories:
1. A chemical that has a median lethal dose (LD50) of more than 50 milligrams per kilogram, but not more than 500 milligrams per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each.
2. A chemical that has a median lethal dose (LD50) of more than 200 milligrams per kilogram but not more than 1,000 milligrams per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between 2 and 3 kilograms each.
3. A chemical that has a median lethal concentration (LC50) in air of more than 200 parts per million but not more than 2,000 parts per million by volume of gas or vapor, or more than 2 milligrams per liter but not more than 20 milligrams per liter of mist, fume or dust, when administered by continuous inhalation for 1 hour (or less if death occurs within 1 hour) to albino rats weighing between 200 and 300 grams each.
So if we simply use the Lethal Concentration (LC) 50 of 200 ppm we have a point on the scale that we can easily define and quantify. The code says HAZMAT with an LC50 less than 200 ppm is “Highly Toxic” and any HAZMAT with an LC50 greater than 200 ppm but LESS THAN 2,000 ppm would be considered “Toxic”. This is the FIRST stage of my evaluation, but it gets me in the correct ball park so I can be sure I am playing in the correct game when I begin to apply my IFC rules to my HAZMAT.
The other reason why I like to use the LC50 criteria is that is stands alone, whereas the other criteria’s definitions are a bit dated and use test data acquired from albino rats and rabbits, which is not easy data to locate and use; whereas the LC50 is much more straightforward and much easier to use:
3. A chemical that has a median lethal concentration (LC50) in air of 200 parts per million by volume or less of gas or vapor
3. A chemical that has a median lethal concentration (LC50) in air of more than 200 parts per million but not more than 2,000 parts per million by volume of gas or vapor
So what is Chlorine’s LC50?
Well, that all depends on who you ask and where you obtain your data! My go-to source for Chlorine data is the Chlorine Institute’s Chlorine Safety Manual, which states the following:
The U.S. National Institute for Occupational Safety and Health 1980 “Registry of Toxic Effects of Chemical Substances” lists the following inhalation LC50s (concentration of chlorine in air lethal to 50% of the test population of the defined animal, exposed over the specified time period):
Human 840ppm/30 minutes
Rat 293ppm/60 minutes
Mouse 137ppm/60 minutes
The lowest concentration of chlorine in air (other than LC50) which has been reported to cause death in humans or animals is listed as 500ppm/5 minutes.
An SDS I was able to find online states:
LC50, Inhalation Gas = Rat 293 ppm 1 hours
But the bottom line appears to be that both sources (highly reliable) state that the LC50 for Chlorine is over 200 ppm and less than 2,000 ppm so that puts it in the “Toxic” category.
Using the 2015 edition of the IFC, Chlorine would fall under three (3) chapters:
CHAPTER 50: HAZARDOUS MATERIALS-GENERAL PROVISIONS
CHAPTER 53: COMPRESSED GASES
CHAPTER 60: HIGHLY TOXIC AND TOXIC MATERIALS (but ONLY for “toxic” requirements)