What is essential for ensuring proper ventilation in a food service establishment?

Regular maintenance and cleaning of ventilation systems are crucial for ensuring proper airflow in a food service establishment. A well-maintained ventilation system helps to remove heat, smoke, and cooking odors, thus creating a more comfortable environment for both employees and customers. Additionally, cleaning these systems prevents the buildup of grease and other contaminants that could affect food safety and hygiene. Proper ventilation also reduces the risk of fires, as greasy buildup can become a combustion hazard if not addressed.

The other options do not contribute effectively to ventilation. Curtains on windows may obscure airflow or prevent it from circulating, candles for scent can introduce unwanted odors and potential fire hazards, and keeping doors open may not be practical or effective for maintaining a controlled and safe environment. Thus, the consistent cleaning and maintenance of ventilation systems stands out as the key factor in achieving adequate and safe ventilation in food service.