Function of Bubble Type Damper

[Angyz]

Why does the bubble type arranged in this manner, what's the function of each?
Hope to get some knowledgeable advice. Thank you!

 

[MintJulep]

It's "bubble tight".

Beyond that, maybe you could tell us just a little about what we're looking at.

 

[SAK9]

The function of the bubble tight damper is to provide extremely tight positive shut off during isolation.It appears in this instance they are meant to isolate a safe change filter located in the exhaust stream of a hazardous facility.The filter may need fumigation before removal and these dampers provide the isolation when the filter is fumigated.