A 28-year-old male operating theatre technician in Mumbai reports a 3-week history of recurrent boils and folliculitis on his neck and chest. He works in the central sterile supply department (CSSD) and is responsible for sterilizing surgical instruments. His colleague mentions that he has been using 0.5% sodium hypochlorite solution to disinfect the CSSD work surfaces and instrument trays for the past 2 months, but the solution has been stored in an open container at room temperature in a dimly lit storage room. Culture of the pustule fluid grows Staphylococcus aureus. The infection control officer suspects environmental contamination from inadequately disinfected surfaces. Which of the following is the MOST LIKELY reason for the failure of sodium hypochlorite to prevent this outbreak?