Cleaning and restoration professionals know that EPA-registered disinfectants must be used exactly according to label directions. This is repeated so often that people become immune to it. But beware, there are important reasons – beyond liability and avoiding fines – to follow labels.
Foreign Object Contamination You rarely hear about destructive contaminants and disinfectants. For example, commonly used chlorine-based disinfectants are very sensitive to contamination. Even a small piece of steel, such as a fragment of a broken staple, can catalyze the destruction of the available chlorine and make the product less effective. The challenge is that you rarely notice when these contaminants come in contact with the product and wouldn't know that the product had been altered.
Don't Mix Solutions Another type of contamination arises when someone tries to “boost” a disinfectant and decides to add a little detergent. This might seem like a good idea, but there's a hidden consequence. Many disinfectants have active agents known as "cationic surfactants." The cationic part of the molecule is what kills the germs. It is positively charged. However, most general purpose detergents depend on an "anionic surfactant," which is a negatively charged molecule. Positive and negative charges neutralize each other. Typically, this makes the solution cloudy. But what you can’t see is that the solution is no longer effective.
There are plenty of other examples of how contaminants destroy disinfectants, so take the label seriously and don't add anything unless the label expressly says you can.