Let is the opposite of Control. Control is a synonym of Contain. Contain is a synonym of Incorporate. 
you are likely to find Sink in/at/on Laboratory. you are likely to find Fire in/at/on Laboratory. Fire requires Oxygen. 
Let <--Antonym--> Control <--Synonym--> Contain <--Synonym--> Incorporate 
Sink --AtLocation--> Laboratory <--AtLocation-- Fire --HasPrerequisite--> Oxygen 