Effects of Time, Temperature, and Humidity on Soil Drying on Medical Devices

In the healthcare environment, delays can occur that prevent reusable devices from being processed within the specified time outlined in manufacturers' instructions for use. It has been suggested in the literature and industry standards that residual soil components, such as proteins, may undergo a chemical change when they are exposed to heat or experience prolonged drying times under ambient conditions. However, little experimental data are available in the literature to document this change or how is may be addressed for cleaning efficacy. This study presents the effects of time and environmental conditions on contaminated instrumentation from the point of use until the cleaning process begins. It demonstrates that soil drying after a period of eight hours changes the solubility of the soil complex, with a significant change occurring after 72 hours. Temperature also contributes to chemical changes in protein. Although no significant difference occurred between 4°C and 22°C, temperatures greater than 22°C demonstrated a decrease in soil solubility in water. An increase in humidity prevented the soil from completely drying and prevented the chemical changes affecting solubility from occurring.