OTS Guardian

In Brief

OTS Guardian, front view
molded, flat visor
Mask frame/
soft body
Respiration nose and mouth
Head harness/
5 straps
Quick removal no
Pressure equalization nose block
Defogging automatic defogging
Purging through 2nd stage
Surface valve yes
2nd stage limited quick release: can only be operated when mask is removed
OTS 2nd stage
Redundancy no
1st stage Aqualung Legend or Apeks XTX100, TX100, XTX50, DS4
Communication optional

En Detail

The OTS Guardian can be often seen in professional use. It looks, well, very similar to the Interspiro MK II and it has the same edged visor form. In contrast to the MK II, the Guardian features the CE marking that quite some buyers in the EC need to obey.

Visor and Mask Body

The OTS Guardian features the typical, almost classical full face mask form: an opaque mask body that avoids unwanted reflexions and the molded faceplate/visor with a planar (flat) front. As it is necessary for molded visors, it is made from resitent polycarbonate. However, the sides of the visor are completely transparent, unlike, for instance, the Dräger PND. In contrast to full face mask designs with a completely planar, tempered glass visor the OTS Guardian builds small. This keeps the overall mask volume low and mask buoyancy is quite okay. Still, view field through the visor is great according to my own experience when diving it for a test.

You can even get the mask frame in different colors, even in pink, if you are so inclined. Welcome, Mrs Darth! I don't know whether they also sell mask warmers.
My experience: The view through the visor of the OTS Guardian is similar to that of the Dräger PND and really good. I haven't noticed any big difference during test diving the Guardian. However, I noticed that the nose section in the visor is really large.


Again, the OTS Guardian follows the traditional design: an inner mask allowing the diver to breathe both through nose and mouth. Breathing gas is first guides across the frontplate in order to help automatic defogging and only then enters the inner mask around nose and mouth. Breathing out, gas directly leaves the masks through the second stage. This second stage is plugged into the center of the mask, yet the stage body itself has been design to extend crosswise in order to minimize the required space in front of your face.

Head Harness and Quick Removal

Again, the OTS Guardian follows the proven design of many successful full face masks with its 5 head harness straps. However, there is no additional quick release mechanism, much unlike the Dräger Panorama Nova Dive. The straps have small stepping so that you can adjust the straps very precise.

Pressure Equalization

OTS Guardian back view,
nose block and red release lever.

Hating to repeat myself I still have to write that when it comes to pressure equalization, the Guardian is just classic. An adjustable nose block just sits below your olfactory bulb. To carry out pressure equalization you grab the mask at its bottom and slighly push it up so that the block blocks your nose. This works quite okay.

However, not everyone will be comfortable with this traditional equalization system, so you should try first before buying this mask. Of course, there is always the (much more expensive) alternative in form of the Dräger PND with its really easy-to-use nose clips.


With the OTS Guardina, fresh breathing gas is first guided across the inner side of the mask faceplate. This is much similar to how most gas masks and respiration protection works. The dry and CO2 depleted fresh gas defoggs the mask quite good and mostly avoids fogging. As many know this works quite good in practise.


Any water entering the full face mask is normally purged through the 2nd stage. There is no separate purge valve.

1st and 2nd Stages

When it comes to the first stage, you have quite some freedom in choosing one. However,  due to its special construction and connector, the second stage must be from OTS:
  • 1st stage: Aqualung Legend, Apeks XTX100, TX100, XTX50, DS4.
  • 2nd stage: OTS Guardian.
As a bonus, the 2nd stage of the OTS Guardian is pluggable. But ... while you can plug it into the mask at any time, even below surface, you cannot release it while waring the mask. You can only release the 2nd stage when you have access to the mask inner. So, this is a quick connector, but not a quick release. Thus, the OTS Guardian lacks the ability to switch to a backup gas system without having to remove the mask first. This is where the Dräger PND clearly excels.


There is no option to add a backup 2nd stage to the OTS Guardian. And you cannot switch regs as the release lever can only be operated after you have removed your mask from your face. It is in no way a real quick release, but mainly a quick connector.

Surface Valve

OTS now sells its Guardian including a surface valve, which is very convenient. This valve sits on the left side of the visor and can be easily operated by screwing in clockwise or anti-clockwise. This way you don't waste gas while on surface after you have already plugged in your 2nd stage into the mask. Remember: you can't unplug the reg until you remove the mask.


OTS is well-known for its underwater communication systems. Even Ocean Reef sells it. Thus, of course, the Guardian has the option of adding underwater communication. Everything else would be a bad joke.

Back to the full face mask overview.