Final answer:
Covering a patient's mouth and nose with a mask when coughing or sneezing helps prevent the spread of airborne diseases like COVID-19. Used tissues should be disposed of in the trash immediately.
Step-by-step explanation:
When an EMT covers a patient's mouth and nose with a mask, the fundamental goal is to help prevent the spread of airborne diseases, such as COVID-19. Covering the mouth and nose effectively with a mask can greatly reduce the risk of transmitting infectious particles through respiratory droplets, which are often released when a person coughs or sneezes. To further minimize the risk of spreading germs, it's important to cover any coughs or sneezes with a tissue, then promptly dispose of the tissue in the trash.