What substances are likely to build up on walls and ceilings if ventilation systems are not effective?

The buildup of grease and condensation on walls and ceilings is a significant concern in foodservice environments, particularly in kitchens. When ventilation systems are not effective, they fail to remove the warm, moist air that is produced during cooking. This moisture can condense on cooler surfaces, creating an environment for grease to accumulate.

Grease is a natural byproduct of cooking processes such as frying, sautéing, and grilling. Without proper ventilation, this grease can settle on surfaces, leading to unclean and potentially unsafe kitchen conditions. The accumulation of grease not only poses a fire hazard but can also lead to pest attraction and unsanitary conditions.

In contrast, while other options may result from poor ventilation, grease and condensation are specifically related to kitchen environments where cooking takes place, making them the most likely substances to accumulate in this scenario. Dust and dirt, water and mold, and smoke and ash are more associated with other types of environments or issues not directly linked to cooking processes.