Need some info regarding Exhaust fan, Single action or double action how to visibly identify?

I just purchased plastic body 8" GFC exhaust fan for my bathroom, I told my local shop keeper that I need “double action” for which he charged me extra Rs.200

After installation I am bit skeptical about my fan i.e how do I know if my fan is single or double action? There is no marking on box there is no info on internet regarding Single or double action and poorly developed Pakistani sites provide no info regarding it

I do know that in theory Single action only allow outflow of air while double action allows inflow as well but I donot know if double action means simultaneous flow of inward/outward flow or it is just a switching position to run this fan in opposite direction

At the moment my fan makes weird noise when door is closed because it seems the air is forcefully trying to come in and if I open the door the the noise stops immediately

If you know any visible difference between these two models then please share your info Thanks

You can’t visibly identify by just looking at the fan if it is single or double action until it is written on the packing of the product. I used to have wahid dou le action exhaust fan that need to be pulled by the rope quickly twice for its double action.

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Noise when using exhaust fan in room with doors and windows closed is fan starving of air, creating slight vacuum in the room.

There are normal exhaust fans which only exhaust air from room to outside, and reversible exhaust fans (which can be switched to intake outside air instead of exhausting air from room). Both functions cannot happen at the same time as exhaust involves motor turning the fan blades in one direction and intake involves motor turning the fan blades in reverse direction.

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Thanks for your reply guys

So it means I have single action fan the rope only has on/off position

but anyways I don’t need double action in this case, However it is so disappointing that the dishonest shopkeeper lied about it

At my previous location the exhaust fan makes no noise probably because the room had plenty of intake channels but at this new location the room had no intake sources therefore I noticed this noise and got confused

I had a 8" bathroom exhaust fan once. Pulling on the rope would allow it’s plastic blades to twist 90 degrees and reverse the direction of air flow.

Simple and effective.

Sheikh ‘Reversible’ Chilli