Dispensing booth also named the weighting booth, sampling booth or downflow booth . 

But no matter which name, due to this kind of air purificaiton equipment inside is always keep negative pressure.

So containment booth normally use in pharmaceutical factory or chemical Laboratory for protect the worker far away harmful gases and Powder dust in operating.  

3 step filtration , the HEPA filter + secondary filter + perfilter for make sure inside keep class100 purification rank. 

10% -15% exhaust air release for per circulate.