Final answer:
The minimum duration hand-operated metering faucets must remain open is usually 10 seconds to ensure effective hand washing according to health standards.
Step-by-step explanation:
The question pertains to the minimum duration that hand-operated metering faucets must remain open in order to comply with health and safety standards. These standards are often specified in building codes or health regulations to ensure that users can wash their hands effectively, promoting hygiene and preventing the spread of disease. The typical regulation requires that hand-operated metering faucets remain open for a minimum of 10 seconds. However, this duration can vary depending on local codes and regulations. To ensure compliance, it's important to refer to the specific requirements of the jurisdiction in which the faucet will be installed.