# Understand grease, cleaning and safety boundaries

Lesson 2 of [Kitchen exhaust cleaning: foundations for buyers](https://greasecleaning.fyi/academy/kitchen-exhaust-buying-foundations.md), 10 minutes.

A clean-looking hood is an observation about a visible surface. It is not evidence about every part of a kitchen exhaust installation. When you buy cleaning, you need to understand the claimed scope and the evidence behind it. This lesson explains why grease matters, how ventilation fits into the pi…

The rest of this lesson is for learners enrolled in the course. [See how Kitchen exhaust cleaning: foundations for buyers works](https://greasecleaning.fyi/academy/kitchen-exhaust-buying-foundations.md).

Also on the [web page](https://greasecleaning.fyi/academy/kitchen-exhaust-buying-foundations/understand-cleaning-boundaries).