MHTSB 2022-01 for (ip) system Emergency Switch

It has come to our attention that under some circumstances the 2ip & 4ip Emergency Bypass oxygen circuit, once enabled, may not shut off again properly and oxygen will continue to flow after the control switch has been returned to the “OFF” position.

This TSB involves 2ip & 4ip systems sold before January 1, 2022.

This behavior can be attributed to excessive restriction in the Emergency Bypass Control (EBC) Switch Exhaust Port Filter fitting, and is alleviated by replacing the fitting with a less-restrictive one.

If you have experienced this problem, please contact us at Mountain High Oxygen and we will send you a replacement filter at no charge, along with instructions for performing the upgrade.

In extreme cases this may not fix the problem, as we have found that additional adjustments to the IPR regulator may be required as the return spring in the IPR regulator may be insufficient to return the emergency valve to the closed position. This adjustment will complement the Exhaust Port Filter replacement.
If this is the case the IPR regulator will need to be returned to have this adjustment made under warranty.

Sincerely, MHO

Note that this problem is also dependent on other aspects of your oxygen system (particularly control tubing length.)  While it is generally only experienced in especially “perverse” circumstances, if you are anticipating servicing your oxygen system you may wish to perform this upgrade at the same time in order to avoid this problem in the future.


MHTSB 2022 01rev 0 (TSB Emergency Bypass Control Switch Upgrade)
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