The Siebe Gorman Puretha was a line of industrial respirators repurposed/manufactured by Siebe Gorman during the early to late 20th century. The Puretha line seemingly was used to market any air-purifying respirators with connecting tubes, including the Mk. IV and V G. S. Respirator models and the Vista Vision.
Disclaimer: This article is based on known knowledge and theory. In-depth research is being conducted and will be included where possible. The writing of this article, and the research project concerning the Puretha, are both works currently being undertaken by the collector "The Commie Waffle". Unless otherwise stated, all information contained within this article should be accreditted to "TCW".
History[]
During the interwar period shortly after WW1, Siebe Gorman started designing concepts that were to replace the SBR as per their contract for the British army, this design would go on to be the 1919 Tissot. However since this design was not adopted, Siebe sold some of these masks off as industrial respirators and the Puretha line had been created.
Jump forward to somewhere during the early years of WW2 and the Mk. IV G.S. Respirator was pulled from service in the British army in favour of the updated Mk. V, subsequently Siebe procured an unknown amount of these masks and repurposed them into Puretha’s.
When the Mk. V G.S. Respirator was pulled from service in favour of the Light Anti-Gas respirator, Siebe again procured an unknown amount of Mk. V G.S. Respirators and converted them to Puretha kits. However, it is predicted that sometime around the late '40s to early '50s Siebe began to run out of Mk. V’s to convert - so in turn they started to produce their own Mk. V’s. (Possibly indicated by the yellow Siebe stamp located on the forehead of the mask.)
During the 1960’s Siebe began producing a panoramic respirator called the Vista Vision as a replacement for the ageing line of Mk. V’s currently in use. Later designs of the Vista reduced the bulk and generally improved the design.
Note: Although the Mk. V widely replaced the Mk. IV and the LAG replaced the Mk. V, there are no confirmed dates of army adoption or Siebe acquisition.
Variants[]
1918 type[]
Main article: Model 1918
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1919 Tissot type[]
Main article: Siebe-Gorman 1919 Tissot
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Mk. IV "General Service" Type[]
The Mk. IV was the first WW2 era Puretha to be produced, based-off the surplus Mk. IV G.S. facepiece with the Type E military spec filter removed and replaced with a jubilee clip and a select Siebe filter. Included in the kit would be some basic items and mask specific kit. It was given to the customer in a metal case with ‘Puretha’ and Siebe’s markings painted on, the colours of these cases vary and have no significance to the mask supplied, it was simply for show - Inside would contain the mask and filter, some webbing to support the canister's weight, an instructional card showing how to don the mask and safety warnings, a mask specific anti dimming outfit, Siebe’s own brand decontamination outfit called ‘Flordol’ and some cotton waste and a brush.
Mk. V "General Service" Type[]
The Mk. V is very similar to the Mk. IV in terms of kit, however, the mask varied in later years. Originally Siebe used surplus Mk. V’s just like its predecessor, the only difference in kit is the anti dimming, it had the same filter, a similar but the same size jubilee clip, the same webbing, the instructional card was the Mk. IV’s due to nothing really changing - both masks had the same straps, hose diameter, donning procedure etc.. - and all the decontamination was the same.
However sometime during the late 40’s to early 50’s it is thought that, as previously mentioned, Siebe began to run out of Mk. V facepieces - thus they had to begin to produce their own facepieces, these can be identified by the yellow Siebe stamp on the forehead of the mask. These were nearly identical to the G.S. facepieces, minus the stamp - though Siebe did produce a white rubber facepiece they are rare and most likely a limited run.
It also seems the Siebe selectively stamped repurposed ones, as of current no notable differences have been discovered between the two, other than the white variant.
Vista Vision[]
The Vista Vision was Siebe’s first design that was not a repurposed or copy of a mask, it consisted of a clear plastic visor clamped onto a rubber mask with the hose and exhale assembly directly attached to the plastic visor. It was a futuristic-looking design and was copied by a few counties including a licenced Dutch 40mm one and a Romanian copy.
There were five iterations of the Vista, all having major or minor differences:
- One with a short hose and G.S. Respirator style head harness - this is considered the original ‘classic’ design.
- Another with a longer hose and reduced size canister - this was an effort to reduce bulk and increase mobility.
- Another with a rubber head harness, the same as used with the GasPro, was produced in white rubber too, again it is rare.
- Another one that used an SCBA/SCUBA/Supplied air unit on the front.
- Prototype versions with a 60mm canister mount.
The kit of the Vista varied from the previous masks. The then brand new masks were supplied in a Siebe branded polythene bag within their storage case, early versions used the same storage case, though later versions used a more modern briefcase-style case. The filter webbing was the same for the original sized canister but had a slightly different design for the reduced size canister. There was also a vinyl plastic webbing presumably for easier decontamination due to chemicals being able to stick within the fabric of the original webbing, the anti dimming outfit was now Siebe branded and the same Siebe decontamination items. A brand new instructional card was supplied with the mask showing how to don the mask and similar safety warnings - the procedure was nearly the same however the update was needed due to it being completely different.
One downfall to its design was the lack of Tissot tubes or oral-nasal cups, so combined with the large clear visor it would fog up badly, the anti dimming did help, but in turn, moisture would collect at the bottom of the mask.
Vista Rama[]
W.I.P
Prototypes[]
Although the design has stood the test of time, by the mid 60's it was sorely outdated and was loosing popularity in favour of other more advanced industrial respirators, Siebe sought to remedy this by updating the Vista Vision to compete with others at the time. In 1964 a short production run of 800 60mm Visa facepieces were sent to the Witton Chemical Company, a further 50 were ordered by Porton Down for testing and trials - the outcome of these are unknown.
Filters[]
The filter of the Puretha was also based on the G. S. Respirator canister design, although the intake was on the bottom along with the inlet valve. It was attached to the mask by the aforementioned jubilee clip instead of wire like the G. S. so it would not require any specialist tools, just a simple screwdriver. There were a total of 15 different filters, all filtering different chemicals. The following table details what the filtration capabilities of each filter was. Use the gallery below to see an example of each of the 15 types.
| Type | Colour | Gives protection against | Chemical formula |
|---|---|---|---|
| 'A' | Blue | Ammonia | |
| 'C' | Black | Acetaldehyde
Acetone Acrolein Arseniuretted hydrogen Benzine Bromine Carbon disulphide Chlorine Diazomethane Diketene Ether Ethylene oxide Formaldehyde Hydrogen bromide Hydrogen chloride Hydrogen fluoride Ketene Phosgene Sulfur dioxide Sulfur Trioxide Sulfur monochloride Sulferetted hydrogen Sulfuryl chloride Thionyl chloride |
|
| 'C.C' | Black with grey stripe | All gases under ‘C’ and particulate smokes and dusts including Cyanide dusts but excluding Hydrocyanic Acid gas. | |
| 'C.G' | Red | Acid gases including Hydrocyanic Acid gas. | |
| 'C.G.C' | Red with grey stripe | Acid gases under ‘C.G’ and particulate smokes and dusts. | |
| 'D' | White | Hydrocyanic Acid gas | |
| 'N.F' | Orange | Nitrous fumes | |
| 'N.F.C' | Orange with grey stripe | Nitrous fumes and particulate smokes and dusts | |
| 'O' | Black with orange stripe | All gases under ‘C’
Cyanogen chloride Methyl bromide Methyl chloride Methylene chloride |
|
| 'S.H' | Red with white stripe | Sulfur dioxide
Sulfur trioxide Sulfuretted Hydrogen Acid gases excluding Hydrocyanic Acid gas |
|
| 'S.H.C' | Red with white & grey stripes | All gases under ‘S.H’ including particulate smokes and dusts | |
| 'B' | Green | ‘All Service’
Carbon monoxide Nickel carbonyl |
|
| 'E' | Blue & White | Ammonia
Carbon dioxide |
|
| 'H' | Blue & Black | Ammonia
Gases under ‘C’ |
|
| 'K' | Red & White | Acid gases under ‘C.G’
Carbon dioxide Hydrocyanic Acid gas |
Filter safety[]
Contents of the Puretha filters are currently unknown, however the UK widely stopped using asbestos in their filters mid WW2, with asbestos completely stopped being used post-1945, thus it is assumed that any filters after that time are asbestos-free. Another risk is leaking filter contents, this can be checked by tapping the filter on white paper, if any black spots presents on the paper or rattling is heard, it is best not to breathe through the filter, the same applies if the breathing resistance is high.
Donning, Safety & Storage[]
Information taken from Siebe Gorman instructional cards.
Donning procedure - As per Mk. IV instructional card:[]
- Place neck sling over the head and fasten body belt. Now place thumbs under first two headbands on either side.
- Put chin well into mask.
- Draw headbands well over the head, so that the mask lies comfortably on the face.
- Test for air tightness as follows: Close the breathing tube for a moment by grasping it tightly with the hands and try to inhale. Inhalation should be impossible. Adjust head bands if necessary.
Donning procedure - As per Vista Vision instructional card:[]
- Place thumbs under first two headbands on either side.
- Put chin well into the mask
- Draw headbands well over the head, so that the mask lies evenly and comfortably on the face.
- Test for airtightness as follows: Close the breathing tube for a moment by grasping it tightly with the hands and try to inhale. Inhalation should be impossible. Adjust straps if necessary.
Safety and storage:[]
Carefully examine all parts to ensure they are in good order. See that the sealing label is removed from the bottom of the canister.
THIS APPARATUS IS NOT to be used IN stills, tanks, enclosed spaces, or in any circumstances where a high concentration of gas is likely to be present.
The above adjustments should be made before the respirator is actually required so that it is ready in case of an emergency. After continual use, the chemical in the canister will become less effective and small quantities of gas will leak through. When this becomes apparent the canister should be renewed.
The mask should be thoroughly disinfected after use.
A special non-irritant antiseptic solution ‘FLORDOL’ is supplied for this purpose.
The mask should be stored in a cool, dry, clean place.
Foreign copies[]
Many countries copied the Puretha either under licence from Siebe or on their own accord, these copies would vary from direct copies to vastly changed designs.
Netherlands[]
Gallery[]
