update

Readme.md

@@ -9,12 +9,47 @@ _**pictures will be added later for more clarity**_
 
 ## 1 - General principle
 
+There was many major version (8 in total) of this gaz mask before arriving at a final design.
+
+### 1.a - Interfacing with the face
+
+The final design relies on an insuflation mask for good fittment to the face of the user. The advantage of this is that the fittment is good, there are mumtiple sizes to choose from, and insuflation mask are readly available (_they are suppose to be single use only, and are used at every anesthesia, CPR and in many other cases_) and **cheap** (_There are some available for arround 2€ at [medisafe.fr](https://www.medisafe.fr/secours/oxygene/insufflateur-bavu/masque-insufflateur-usage-unique.html#MA285-2612-TAI1140_) for example_). 
+
+The downside of this method are that firstly these mask tend to deteriorate over time and with use as they are ment to be single use item, however they are obviously swapable so they can be switched when unsusable ; and secondly that the height of these mask and the length of the adapter puts the majority of the mask weight far from the face and thus a bit unconfortable, espacially under quick head movments.
+
+For a mask that directly fit on the face, see (the section on older version)[2 - Older version].
+
+### 1.b - Filtering cartidge
+
+This mask supports standard 40mm threaded cartridges - sometimes also known as "_nato threaded_" cartridges - which the standard dimensions are defined in [sources/dimensions/nato_thread_spec.png](./sources/dimensions/nato_thread_spec.png).
+
+We also provide a 3D printed cartridge following this standard and compatible with this mask and other standard gaz mask in the [3D-printed-parametric-respiratory-one-way-valve](https://git.deuxfleurs.fr/distorsion/3D-printed-parametric-40mm-gaz-mask-canister) repository, which is a submodule of this repository located at [./3D-printed-parametric-respiratory-one-way-valve](./3D-printed-parametric-respiratory-one-way-valve).
+**WARNING : _Please don't use a 3D printed cartridge (or even our mask) in life threatening situations !_** Or at least understand the inner working of gaz mask and test your gaz mask (_especialy its fittment to your face_) before using it.
+
+There is also an older version of such a cartridge modeled within the file of the [old gaz mask version]( 2.b - _Older version :_ Filtering cartidge).
+
+There also exist 3D printed adapter from this standard to other standard gaz mask connector if you search on 3D printing site.
+
+### 1.c - One way valve(s)
+
 _TODO_
 
 ## 2 - Older version
 
 _TODO_
 
+### 2.a - _Older version :_ Interfacing with the face
+
+_TODO_
+
+### 2.b - _Older version :_ Filtering cartidge
+
+_TODO_
+
+### 2.c - _Older version :_ One way valve(s)
+
+_TODO_
+
 ## 3 - Explanation of parameters
 
 _TODO_