This simple but very effective bottle for liquid aromas is also a very effective way of breath control:
Connect this mini-bubbler bottle simply directly, or with the hose of your gas mask, and fill it with a liquid of your choice, usually water.
The liquid increases breathing resistance and the bubbling sound is an added effect. The more liquid you fill, the more you have to strain to breathe.
The small air inlet tube goes all the way to the bottom of the bottle, making it a real mini bubbler bottle.
You can of course fill this bottle made of black anodised aluminium with other liquids of your choice, and also add a few drops of this or that.
The bottle has a 40mm standard thread.
Please note that solo breathing sessions are not without danger. Therefore, never play alone or leave your partner unattended.