I was called by email to visit to a school foodservice department to help them with a problem in sanitation practice. I learned they had been told upon inspection that their triple-sink disinfection compartment sanitizer and in-service table cleaning solution were below 50 ppm. These contacts are priorities, of course, so I was soon on-site.
The kitchen manager told me the inspector instructed them to to add chlorine to their table sanitizer bucket as well as their triple sink compartment for sanitizing until the reading was above 50 ppm. The problem with this procedure is that the school was using a quaternary disinfection system both for dishes and tables. The kitchen manager said she was hesitant to tell the inspector she suspected they were using the wrong kind of strips to test the solutions.
This error could have had greater ramifications than just wasting a batch of disinfection solution. When mixed, quaternary agents and chlorine can produce a dangerous reaction, including toxic fumes. It is not possible to test quaternary effectiveness with methods designed to measure chlorine.
Fortunately, nobody was hurt on this day. However, across the country each year, many are not that lucky. When chlorine is mixed with other cleaning chemicals, the results are often similar to what they were in WWI, when chlorine gas was first used by Germans very effectively against the Allies on April 22, 1912, at Ypres, Belgium. Allied troops were decimated.
There are limited and very specific times when chlorine and other chemicals are legitimately introduced into a solution together, and usually not one right after the other. Make sure to follow - very carefully - labeled instructions on both products about how and when to do this if it is part of a cleaning procedure.
Don't make a lethal mistake by mixing chlorine with other chemicals - even if you are told to do so by an inspector. There has likely been some miscommunication or mistake made, and asking questions is completely appropriate. Know your products, question instructions you suspect are in error, and be safe with chemistry for everyone's health.