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Wednesday, October 26, 2011

Some Rules Aren't Made for Breaking

I’ll admit there are times when I don’t follow “the rules” and I have been known to push boundaries. At the same time, however, there are situations when I always follow “the rules”, but the only two that come to mind are baking and playing with chemicals. Unlike cooking, where you can simply throw a number of ingredients together and simmer, stew or bake with periodic tasting to adjust for flavor profile preference, baking is almost mathematical in precision. Anyone who bakes knows if you leave out the egg, the baking soda, add too much liquid, over mix or over kneed you can quickly ruin whatever cookie, cake or pastry you were preparing. I happen to know from experience if you leave the egg out of the brownie recipe, no amount of dipping in hot tea or coffee is going to get that thing to soften up!

Like baking, playing with chemicals has very specific rules that need to be followed some are hard rules for safety sake such as do not mix oxidizers together, do not mix chlorine with acids, don’t mix chlorine with ammonia, don’t mix acids and bases together….the list can go on and on. The list of Do’s & Don’ts should also include don’t ignore the label instructions by over or under mixing the cleaners and disinfectants that we intend to use.

As Lee and I have attempted to describe in our blogs, the use of disinfectants takes more than just the consideration of what a product kills. A key consideration is appropriate dilution and with that consideration of a product’s shelf life once diluted. Disinfectant manufacturers provide dilution instructions for a very specific reason, and it is not just to please Health Canada or the US EPA. The dilution instructions provide the ratios and therefore the In Use Solution concentration that a product should be used at. This is the concentration that the product’s efficacy has been tested and approved by the appropriate regulatory body and this is also the concentration that the required toxicity data and subsequent MSDS information is based on. It is also the concentration that the shelf life, once diluted has been determined.

Over diluting of a product means you are using less chemical than necessary to achieve the label kill claim and this leaves you open to the chance that the pathogens you are concerned with are not going to be killed. Inversely under diluting means you are mixing the disinfectant too strongly, and contrary to what many of us believe more is not necessarily better. Additionally, as I hope everyone who uses a concentrate that requires dilution before use knows, once the product has been diluted into a closed container there is a shelf life that has been determined by specific test methodology that needs to be adhered to in order to ensure product efficacy.

This leads to the importance of using test strips to ensure that the disinfectant you are using has been mixed correctly. It is important to understand first and foremost that as chemicals are different in nature so too are the test strips you will use. A QUAT strip cannot be used to test a H2O2 or Chlorine-based disinfectant, so before starting to test, make sure you have the test strip that is designed to test the product on hand. Secondly, know the dilution you are using and what the expected parts per million or ppm of the active chemistry you are testing. Thirdly, know the shelf life. Test strips are NOT designed or intended to extend the shelf life of a product beyond that recommended by the manufacturer regardless of what the test strip reading is. Fourth, is your intention to use the test strips to verify the product has been diluted correctly, use them to verify that the solution is the bottle is still appropriate to use or a combination of both and then determine the frequency with which you intend to test.

For registration purposes, a manufacturer has to provide data to support the shelf life claims so the “hard work” so to speak has been completed for you and many facilities simply choose to spot check dilution systems to ensure for dilution accuracy (more about that next week from Lee). However, there are times, as specified by Best Practice Guidelines or Public Health Inspectors where products are to be tested daily (such as in an outbreak situation) or hourly (such as in a three-sink sanitation system in a restaurant). There is no hard and fast rule that must be followed, simply put, you want a method to validate for quality control purposes, you want a program that suits the needs of your facility and if required you want a program that meets the needs of your local public health inspector to avoid citations.

That leads me to the last point, if you are using a Ready-To-Use Liquid, the expiry date that needs to be followed is that listed on the bottle. There is no need to test the concentration. If you are using a wipe, again follow the expiry date listed on the bottle. You cannot test the product concentration of a wipe – and yes, I have been asked how to use a test strip to determine if a wipe is still at the appropriate concentration…..

Bugging Off!


  1. Thanks for your comments, Nicole. Certainly, dilution rules need to be followed to achieve the label kill claim.

    I think an equally important rule -- and probably one that is even less often followed -- is label contact time. If the label says 10 minutes and the user bends that rule to a one minute contact time to conveniently match the disinfectant's dry time, the potential health, financial, and legal consequences are real and they're significant.

    My cookbook says leave the brownies in a 325 degree oven for 33 minutes. That's exactly what I do, and they're to die for!

    Craig Cheyne

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