One of the worst things to do is mix chemicals, even in janitorial and cleaning fields. Products that are safe on their own can react when combined and released toxic gases within seconds. Bleach mixed with ammonia produces chloramine vapors, and bleach mixed with acids, such as some toilet bowl cleaners, vinegar, or descalers, releases chlorine gas. These gases can burn the eyes, throat, lungs, cause coughing and difficulty breathing, and in enclosed spaces can cause severe injury or death. Mixing two cleaners will not make the cleaner stronger.

Preventing these accidents starts with training and good work habits. Cleaning professionals should never mix chemicals unless the manufacturer's label specifically says to and should always read labels and Safety Data Sheets (SDS) before using a new product. Chemicals should be kept in their original containers or in properly labeled bottles and diluted only as directed. Rinse surfaces thoroughly between different products, work in well-ventilated areas, and wear the recommended protective equipment such as gloves and eye protection. If a reaction occurs, leave the area immediately, get fresh air, warn others, and call for help. Every cleaning employee needs to understand chemical hazards because one moment of carelessness can endanger the worker, coworkers, and the customer.