Protecting the face with a ventilated mask?

 

There was a long running argument about the minimum requirement for face and eye protection in demining. To read my side of this debate, click here.

In 2005 ROFI, the suppliers of the most used protective equipment in HMA, held a workshop in Norway where selected people were invited to agree the specifications for a revised visor. I attended without high expectations, but the design team seemed competent and ROFI were on hand to arrange manufacture, so I left that workshop feeling cautiously optimistic.

One part of the specification that I did not like was the requirement that the protection level of any new material used should be greater than that offered by 5mm polycarbonate. If that could be easily achieved, that was OK, but I felt that the material should not be allowed to dictate the design. They smiled and ignored me because, as is obvious in retrospect, the material had already been selected and the whole exercise was designed to get that material in use.

Accident evidence (and many empirical tests) indicate that untreated 5mm polycarbonate worn correctly and in good condition can protect from an anti-personnel (AP) blast mine at 60cm. Nothing would reliably protect against a bounding fragmentation mine (Valmara, OZM or PROM) at that distance - so this was to be a blast visor (as required in the IMAS).

In Geneva in 2007, ROFI showed me a prototype. At the same time they gave me an armour with a visor attached to the front (an idea I first prototyped many years before) to comment on. The armour with attached visor is not quite right - but the next one might be. The main problem is that there is too much visor - making it impossible to wipe sweat from your forehead or scratch your nose. But the principle is sound and the protection is comfortable. It may be worth making a Mk 3 design, but no one has yet.

By contrast, the new ROFI mask already looked promising. I took it to the field and recommended its trial. It is smaller than a visor, lighter and well ventilated.

However, there were problems...

The mask material is a new and a very lightweight composite - offering higher fragmentation protection than 5mm polycarbonate. The eye-piece is still 5mm polycarbonate and any armour is only as strong as its weakest part so there is no real advantage in the mask being tougher than the eyepiece. I asked why it was, and was told that the material has to be that thick to prevent its edges getting damaged in transit. It is formed under great pressure which makes the layers bond together, but the edges can be frayed with a thumbnail. Sealing them would surely have been easy?

The limited polycarbonate panel meant that I could not see my own feet easily and my peripheral vision was restricted. Not seeing my own feet meant that I sometimes could not see the lane marking, and this is obviously undesirable.

Like many others, I gave ROFI some feedback on the design limitations - and understood that they were going to make some changes.... A year later, I wore the mask for several days in the field. The first thing that became obvious was that the designers had barely changed the prototype.

1) Originally there had been a tiny gap beneath the lens through which blast could enter. This had been changed by tilting the top of the same lens forward. This has left a wide gap at the top through which dust settled on the inside of the lens while I worked. It also moved the lens away from my eyes and seemed to have introduced a problem with reflections.

2) Peripheral vision was still very restricted.

3) The width of the mask dictated the size of my head and there was a constant pressure on the sides of my head that was irritating. 

4) The head strap was still woven in-and-out at the top of the front of the mask - not a good place to make two holes - and this could have easily been avoided.

5) The finish of the mask material (edges of the new material) could still be delaminated with my thumb-nail - which did not give confidence about its long-term durability.

6) The cheek-pads got slimy with sweat and marked my face.

7) Because no one could see that I was trying to talk to them, the mask had to be taken off for all voice communication.

8) I had no doubt that the wearer would have their nose struck by the mask in any real close-up blast event - and could not see why this must be so. I advised that the thing should stand further away from the face, allowing impact with the chin before the nose... as a visor does.

Because the designers (not ROFI) won a design award in Norway they seem to have believed that their job was done. It really is not. What we have is a prototype design - not a finished product. After three days I was really glad to get hold of an old full-face visor and stop feeling blinkered and uncomfortable - as if I had stepped straight out of the Texas Chainsaw Massacre. This is me trying to see my feet in the desert.

There were two people with field experience at the design workshop in Oslo. The second was with me in the desert and we both agreed that the current mask is no better than a 'work-in-progress'. Give us a simple visor, please. [And no, I do not recommend that body armour or those silly marking sticks either, but you have to use what the managers have already bought.]

I recommend that people avoid buying the ROFI masks until you have done your own acceptance trials (not in the office!). Remember, you can get more than four standard visors for the price of each ROFI mask so I advise staying with a conventional full-face visor.

In March 2008, impatient as ever, I used some of the old visors I have had lying around for ten years (since I perfected the catenary forming method) to make this...

This is a deminer in Angola wearing a prototype AVS Mask visor - the result of an experiment to see whether it was possible to make a well vented mask visor using the same material and manufacture methods as the old visor.

1) All parts use a natural curve forming method (catenary) so do not need expensive moulds.

2) The weight can be 10-15% less than that of the standard full face visor (it is narrower and trimmed creatively).

3) It is not possible to steam it up.

4) Peripheral vision is as good as with a full-face visor, possibly better because the eyepiece is closer to my eyes, reducing possible distortion and inner reflections.

5) A revised head-frame to visor attachment reduces possible "wobble".

6) Other people can see when I am trying to talk to them - and the sound of speech vents from the visor well.

7) The material used is 5mm untreated polycarbonate - the same as the normal full-face visor - which is much less expensive that the ROFI mask laminate.

8) It is possible to lengthen or shorten the whole visor face to prevent the bottom hitting the chest of short people. Thoughtful overlaps make it impossible to open the "vents" wide enough to inadvertently introduce a blast-entry gap.

9) There is more material and more work involved than in making a conventional visor - and there is some waste material - so the cost over a conventional visor would go up. But not by much.

10) The slight inner curve at the bottom makes throat and lower face protection better - and hits the face if the visor is raised, so preventing it being raised (I hope). (An either 'on or off' visor is preferred because of the high percentage of accidents in which a visor is raised and supervisors failed to notice.)

I published this on a demining forums and asked if anyone could optimise a design and make them, suggesting that ROFI might like to. In May 2008 I was told that a UK university was making a version in Cambodia, but I heard no more of that.

So in November 2009 I made a finished polycarbonate mask myself. The picture shows a female deminer wearing an AVS polycarbonate mask in Sri Lanka while demining using the REDS system.

The ROFI mask has featured in some recorded AP blast mine accidents - both raised (sitting on top of the head) and down. In one accident in which all witnesses say that the mask was being used properly, the deminer's face was sprayed with environmental fragmentation which somehow got under the mask. This could only have happened if the mask was lifted up by the first fragments to reach it. I asked ROFI for an explanation and it transpired that they had never blast tested the mask. They apoligised for the oversight and had the ROFI mask blast-tested at CTRO in Croatia. It passed, but the test did not include evaluating whether the mask could be lifted.

I think the ROFI mask is unsafe in several ways - and believe that the material is a real constraint on improving the design.

However, with the exception of the Norwegians (some of whom seem to feel obliged to use the mask because it was designed in Norway) most demining groups seem happy enough with a polycarbonate visor or goggles. They seem to have come to the same conclusions as I did.

Today, the ROFI mask is still being sold and, as far as I know, no one is actually making my AVS polycarbonate mask. I use one every time I use my chainsaw but I take a standard visor into the minefield.

 

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