“Ignorance is not too dangerous. If you combine it with power, then this is a toxic mix.” — Yuvai Noah Harari
Not surprisingly, eighteen of the thirty incidents in Volume 3 of the Chemical Safety Board’s series on incident reports addressed incidents at refineries and large chemical complexes. One incident in Volume 3, though, was at a Memphis brewery. The incident sent 10 employees to the hospital, three of whom were admitted for treatment.
What kind of process safety incident could occur at a brewery? Especially, what kind of brewery incident could result in mass casualties? Or for that matter, any facility producing beverage alcohol? Or other products?
The Incident at Blues City Brewery
On Tuesday, February 1, 2022, the person who routinely prepared clean-in-place (CIP) solutions was not available. There were two solutions that needed to be prepared—Dibac and Dilac—and the person assigned to prepare the solutions hadn’t been trained on the difference between them.
According to its SDS, Dibac is a 10% solution of sodium hypochlorite, also containing ~7.5% sodium chloride (table salt) and between 0.1% and 1% sodium hydroxide (caustic or lye, presumably added to adjust pH). For those that don’t immediately recognize it, sodium hypochlorite is the active ingredient in bleach. Household bleach generally contains 5% sodium hypochlorite. When it comes to reactivity, the Dibac SDS states that it is “not applicable,” and while the SDS states that Dibac “may vigorously react with acids resulting in spattering and excessive heat,” and that materials to avoid include acids, strong acids, ammonia, it also states that no hazardous decomposition products are “reasonably foreseeable.”
According to its SDS, the other CIP solution, Dilac, contains ~40% nitric acid and ~6.5% phosphoric acid. Both are strong acids.
The new operator at Blues City Brewery inadvertently charged Dilac (the strong acid) into the 330-gallon Dibac solution tank (the bleach solution). There was a vigorous chemical reaction that released chlorine gas, a deadly poison.
Blues City Brewery was fortunate that no one died in the incident. Still, OSHA cited the brewery for 12 violations and a total initial penalty of $22,000, later reduced to $15,600.
A similar incident in 2019 didn’t turn out so well.
The Incident at Buffalo Wild Wings
On Thursday evening, November 7, 2019, Ryan Baldera, the General Manager of the Buffalo Wild Wings ordered the evacuation of the restaurant—employees and customers—as he attempted to squeegee up a spill of “Super 8” cleaning solution that had combined with a previous spill of “Scale Kleen”. “Super 8” is a 10% solution of sodium hypochlorite. “Scale Kleen”, made by the same manufacturer, is a solution of phosphoric acid (~25%) and nitric acid (~20%).
The two cleaning products reacted to form chlorine gas, which killed Ryan Baldera. Sure, OSHA cited the employer, JK&T Wings, Inc. for 14 violations and initially cited them for a total of $76,265 (later reduced to $50,000). And sure, JK&T went out of business. Regardless, though, Ryan Baldera remains dead although many consider him a hero for his quick action to evacuate and save employees and customers.
Don’t Mix Bleach with Other Cleaning Products
There are frequent warnings about not mixing household cleaning products. Good Housekeeping tells us that there are “11 Cleaning Products You Should Never, Ever Mix”. Even the journal, Business Insider, had a piece, “Cleaning Chemicals Not to Mix at the Risk of Creating Toxic Gases”. These chemicals are not just used at home, however. In a commercial or industrial setting, they are often more concentrated, making the hazard of toxic gases even worse.
The property that makes cleaning products so powerful is their reactivity. They go after contaminants with vigor. It is this same vigor that makes them so hazardous.
Sodium hypochlorite, NaOCl, the active ingredient in bleach, is a strong oxidizer and is very reactive. The reactions in both the Buffalo Wild Wings and the Blues City Brewery incidents were of sodium hypochlorite with acids. The acids happened to be nitric acid and phosphoric acid, but any acid would have sufficed. Even the acetic acid in vinegar.
Bleach + acid → Chlorine gas + water + sodium salt of acid
Dangerous reactions with acids are not the only hazards of bleach, however. Its reaction with ammonia generates chloramines (monochloramine, dichloramine, and nitrogen trichloride).
Bleach + ammonia → monochloramine + dichloramine + nitrogen trichloride + caustic
It is commonly reported that bleach reacts with isopropyl alcohol (rubbing alcohol) to generate chloroform (CHCl3) and the sodium salt of acetic acid.
Bleach + isopropyl alcohol → Chloroform + sodium acetate
What is not reported so often is that bleach also reacts with ethyl alcohol to generate chloroform and the sodium salt of formic acid.
Bleach + ethyl alcohol → Chloroform + sodium formate
Don’t Mix Hydrogen Peroxide with Cleaning Products
There is one more bleach reaction worth mentioning, and that is its reaction with hydrogen peroxide. Bleach and hydrogen peroxide are both oxidizers. Fortunately, when they react, they DO NOT form a toxic gas. Instead, they form oxygen. Oxygen is not toxic, but it promotes corrosion and flammability. For instance, the flammability limits of ethanol are 3.3% to 19% by volume in air. When the oxygen concentration increases, the flammable range widens. The lower flammable limit of ethanol does not get much lower, but some report the upper flammable limit of ethanol at 60% or more (67.9% per Crowl and Louvar, Chemical Process Safety, 3rd Ed., p. 259). Regardless, in the presence of higher oxygen concentrations, any flammable vapor will ignite much more easily and burn with greater intensity.
There is another caution about hydrogen peroxide: do not mix it with vinegar. The two compounds react to form peracetic acid which is both an irritant and highly corrosive.
Toxicity of the These Gases
The comparative toxicity of these gases are shown in the table below. The U.S. Occupational Safety and Health Administration (OSHA) has established permissible exposure limits for some substance, but not all. The case of peracetic acid, the table shows the PEL established by the state of California. PELs are the levels below which employees may be exposed. Another hazard level is Immediately Dangerous to Life or Health (IDLH), established by the National Institute for Occupational Safety and Health (NIOSH).
In 2023, the most recent year for which the National Poison Data System lists data, there were almost 150,000 human exposures to chemical cleaners reported in the United States. These were mostly household exposures, but there were thousands of workplace exposures as well. The potential for toxic exposure as the result of working with cleaning products cannot be overstated.
Training—Our First Line of Defense
It should go without saying, but apparently cannot, that people should not mix cleaning products, especially if one of them is, or contains, bleach. What’s true for household cleaning products is doubly true for commercial or industrial products; they tend to be more concentrated.
Beyond that, personnel need to be trained on the hazards of the cleaning products they are using. In both the restaurant incident that resulted in a fatality and the restaurant’s closing, and in the brewery incident that put people in the hospital, OSHA cited the businesses for failure to train employees on the exposure hazards in their workplace, as required by the Hazard Communication standard. It is important to note that a cursory review of the SDSs would not have been sufficient to train employees on the hazards of mixing the bleach product with the nitric/phosphoric acid, because none of the SDSs were specific about that hazard or its severity.
The Attention They Deserve
As safety professionals, we are often so focused on the hazards of our production processes that we overlook the hazards of ancillary tasks, like cleaning. Yet these hazards can also result in severe consequences, including death. Let’s make sure we give them the attention they deserve.
