I found a very simple but effective solution.
Unfortunately Mods obviously don't want me to post off topic (
>>16253016 (You) "file deleted")
So I'll give my best to describe what I did:
So solution I found doesn't even involve my new gasmask. I took a common gasmask accordion hose and removed the thread on one end.
The GDR gasmask as seen in
>>16251492 (You) has a two valve exhalation system. I removed the outer valve and stuffed the accordion hose into the outer exhalation hole. This solution is airtight, the hose stays in place (the wrinkles hold it in place) without glue and the modification is reversible because no damage was done to the mask.
Although the new mask is useless for this project it is a beautiful mask and I don't regret buying it. It's the model from this picture
>>16249432 (You)
I will take some pictures during the next few days, when I meet my gf and we have time for some playing.
Thank you for your interest, tips and patience.
Maybe we can get a little storytime started?
>What do you like about gasmasks?>How did you come across gasmasks as a fetish?>What are your experiences/fantasies with gasmasks? 
