Guide: Modifying the S10/FM12/FMJ-08 Gas Mask

Hey All,

Welcome to this guide on Modifying an S10. This guide is written with the idea you are planning on converting your mask to the KB3D Nexus system or changing the side valve. Now this guide has previously been written on my old website, which included how to change the side valve and eye ring. I no longer provide the eye ring, however I have left that guide at the bottom of this page.

This guide is valid for the S10, FM12, FMJ-08 gas masks. 

Before you begin

The original guide was written around modifying an S10 without the specialised servicing toolkit. Working without the correct tools makes damage more likely, and some modifications may be difficult or impossible to reverse. So, firstly we do not take any responsibility if you damage your mask. Second, be prepared for this modification not to be reversible. 

Nexus Modification (removing the front valve)

So this portion of the guide will cover how to remove the front valve assembly, and how to insert the Nexus Insert. 

Why would you do this? - the Nexus system is designed to allow you to simply swap in and out modules on the front of your gasmask. To do that we introduce an "Nexus Insert". this device provides a screw thread for modules to be screwed in an out of.

Disclaimer: this next step should be done with the official tool. However as I don't own one. this is how I modify masks. You are responsible for any damage to the mask.

1. To remove the front valve we first have to access the black plastic retaining ring.This ring sits on the inside of the gasmask surrounding the valve assembly. To remove the black plastic retaining ring, I use a a blunt table knife (butter knife etc - flat metal but not sharp) and position in between the rubber of the mask and the solid black plastic ring. Don't be tempted by the groove which is in the middle of the ring, the metal needs to be touching the rubber of the mask. Then you need to gently twist the flat metal tool to pry off the black ring. It can be a little tricky and be careful not to damage the rubber of the mask. 
2. Once the ring has been removed. then push from the inside the whole valve assembly out of the mask. 
3. Now insert the Nexus Insert and secure it with the nut from the inside. - Note the nut is on a reverse thread. So it spins the opposite way.

Changing the side fittings

It’s a common misconception that the S10 has only one side valve. The speech unit on the left hand side of the mask, is the same diameter and connects the same way as the right hand valve. Therefore it is possible to modify both. 

This guide will show you how to replace only the right valve. The left speech unit can be replaced with the same guide.

The valve is held together with what I call a ‘snap’ connector. That’s simply a black plastic ring which is pushed over a ridge and that “snaps” shut. For the side valves this ring is found on the inside of the mask. It might be difficult to find as the inner rubber nose and mouth guard might be in the way. If you plan to use the S10 modules, then it might be a good time to remove that rubber mouth guard now. See below on how to do that.

Once you have found the valve, to remove the black plastic ring, use a large flat headed screw driver/ or butter knife, to gently position it between the rubber of the mask, and the solid black plastic of the valve. Then gently by twisting your tool  you can gently pry off the black ring. 

Don’t be fooled by the groove in the plastic ring. It’s a red herring. It needs to be between the rubber surface of the mask and the solid black plastic valve.

Once that ring has been removed the valve should pop out. 

Keep the valve and ring. Especially the rubber membrane, which can be easily pulled out. 

To insert the KB3D valve. You simply push the valve in and then use the nut to tighten it. To ensure it’s really tight, I use a pair of pliers to twist the valve to make it very tight.

Tip: when screwing in attachments to the KB3D side valves, you might be tempted to screw it tight. If possible it’s best to avoid screwing it tight as you might run the risk of unscrewing the valve instead of the attachment. I’m still working on this issue to try and stop it from happening.

Returning to original side valve.

This is difficult to do. However you simply unscrew the KB3D valves. Then push the original back in. The most difficult job it to push the black ring back over the ridge. I personally have not managed it yet.

Therefore, this is one of the potential irreversible modification.

Replacing the outer eye rings

To replace the eye ring, you simply need a a flat and strong tool. I personally use the spatula picture below. Originally used to remove printed items from the print bed. A butter knife should also work. 

The lens assembly contains 4 parts:

Outer ring is what is replaced by the 3D printed part. The remaining components do not need to change. However I will show you how to assemble it below.

Returning to the original ring

Repeat the above steps but with the original ring. I personally found the original rings very difficult to get back on. Whiteout on YouTube has a great guide on this.