The Gas Diffusers used in the PanLab Langendorff and Organ Baths are very small and need to be well maintained in order to prevent blockages.
It is ideal to keep a low stream of gas running through the diffuser during the standard cleaning protocol for your bath. This prevents solutions being sucked back into the gas line, which may cause blockages if they are allowed to dry.
If there is no gas passing through the diffuser or a very poor supply, the diffuser can be removed and soaked in warm water. You can then try to manually pass some air through the diffuser with a syringe to try and dislodge any build up of salts. This application should be very gentle so no damage is caused by excess pressure.
If the diffusers need to be replaced, these can be purchased from your local ADInstruments' representative. The relevant part code is SP3777.