McDonald's

Official wording

Provide exhaust hoods to remove toxic gases, heat, grease, vapors, and smoke and be approved by the local building department. Canopy-type hoods shall extend 6 inches beyond all cooking equipment. Toilet rooms shall be vented to the outside air by a screened openable window, an air shaft, or a light-switch activated exhaust fan, consistent with local building codes. Adequate lighting shall be provided in all areas to facilitate cleaning and inspection. Light fixtures in areas where open food is stored, served, prepared, and where utensils are washed shall be of shatterproof construction or protected with light shields.

In plain English

Cleaning products, pesticides, or other chemicals were stored or labeled in a way that could let them get into food. This is serious because chemical contamination can make people sick quickly.