Final answer:
Face masks are placed on infected patients who are symptomatic to prevent the spread of their infected secretions to others.
Step-by-step explanation:
Face masks are placed on infected patients who are symptomatic to limit dissemination of their infected secretions to others. When a person is symptomatic, it means they are showing signs and symptoms of a disease or infection. By wearing a face mask, the infected person can prevent the spread of respiratory droplets that can transmit the infection to others.