A surface where blood or microbes are present is considered:

A surface where blood or microbes are present is considered contaminated because contamination indicates the presence of harmful substances, such as pathogens or organic matter. In the context of infection control and health care settings, a contaminated surface poses a risk for the spread of infection, as it may harbor bacteria, viruses, or other microorganisms that can lead to diseases.

In contrast, a clean surface has been free of visible soil, while a sanitized surface has been treated to reduce the number of microbes to a safe level. Risk-free would imply no possibility of infection, which would not be the case with a contaminated surface. Understanding these distinctions is crucial for maintaining a safe and hygienic environment in healthcare settings, where proper cleaning and sanitization practices are vital to prevent the transmission of infections.