Monday, August 3, 2020

HEAD/MARES Comment On Recent Snorkeling Deaths In Hawaii


Since the release of a number of Full-Face Masks (FFM) at DEMA in 2015, they have exploded in popularity with snorkellers worldwide.  The masks make snorkeling feel much more natural due to a number of features including anti-fogging and the ability to breath through your nose (rather than your mouth with traditional snorkels).

There has been a growing concern over the safety of a number of these masks.  After a recent spate of deaths of tourists in Hawaii, some of which were related to Full-Face Masks.  HEAD/MARES – one of the manufacturers of full face masks – has started working with local Hawaii authorities to understand how these deaths have occurred and if there is any relation to Full-Face Masks.

With very little information available on the type and makes of the masks worn by the snorkelers involved in the accidents, HEAD/MARES have taken on specialized testing of various types of masks on the market to help determine contributing factors to the drownings.  The testing involves measurement of potential CO2 buildup.  This form of testing requires some specific machinery in the form of an ANSTI machine which HEAD/MARES have in-house in their rebreather manufacturing center in Belgium.

As background to their testing, HEAD has stated:

“While there are no specific standards for testing of full-face snorkel masks, HEAD referenced two European Union Norms, the EN250, and EN14143, standards widely used in the scuba diving industry and also adopted by US authorities such as NASA for the testing of full-face scuba diving masks.”

“CO2 buildup measured on the HEAD full face mask is at around 50% of the maximum allowed limits set by EN250 at a breathing rate of 10 liters per minute (slow and calm breathing) and at around 20% of the maximum limit when breathing at a rate of 62.5 liters per minute (e.g. breathing heavily with still deep breaths in a panic situation).  In other words, the higher the stress level, the higher the breathing rate, and the better the mask performs.”

“The success of the HEAD full face snorkel masks has spawned a number of low-cost copycat masks from little-known companies whose expertise, design and manufacturing experience are unknown.  These off-brand products are offered at attractive prices, but their performance and the nature of any research or testing that stand behind them, if any, is completely unknown.”

The results from the HEAD testing of a number of products can be seen below.  As you can see, three of the four full face snorkel masks exceed the EN250 standard for CO2 exposure at low breathing rates, but they are all within limits for high breathing rates.

Extract From HEAD Watersports Full Face Mask Testing Results
Extract From HEAD Watersports Full Face Mask Testing Results

HEAD has reached out to the Maui Department of Fire and Public Safety and Hawaii State Dept. of Health and offered to assist in their investigations.  Among other things, HEAD has provided its test results to the lead investigators in the Hawaii Dept. of Health and the U.S. Consumer Product Safety Commission, and it has offered the use of its test facility and other assistance.

At this point, it is not clear what caused the recent drowning deaths in Hawaii.  The only common factor other than the deaths occurred in the water was the age of the victims:  10 of the 11 drowning victims were men over the age of 50.  Of the victims, two were scuba diving, three were using two-piece snorkel gear, two were swimming, two were using full face snorkel masks, and one was fishing from a jetty but found floating in the water.

It seems that more facts are needed to be able to draw any conclusions.  However, it is to be noted that snorkeling, swimming, and other activities in ocean waters involve elements of risk, particularly to inexperienced and unsupervised swimmers who are not familiar with local waters or who may not be physically prepared for vigorous activity, but these risks have nothing to do with full face masks.

You can see a number of the masks on display from the coverage of DEMA 2015 below.

Stephan Whelan
Stephan Whelan
Stephan is the Founder of His passion for the underwater world started at 8 years-old with a try-dive in a hotel pool on holiday that soon formulated into a lifelong love affair with the oceans. In 1996 he set up and helped grow the site to be one of the largest diving websites around today.


  1. Stephan,

    We on the Scuba Accidents and Risk Management for Divers Facebook page are discussing your article on testing by Mares of their full face snorkeling mask. I am a diver/retired dive instructor from way back, and also a retired industrial hygienist and safety professional.

    This article mentions the EN250 standard, without giving the actual standard for breathing air CO2. Could you enlighten us as to the actual standard says?

    The chart above does not give the units for the results. It states that the EN250 standard for CO2 at 10 liters per minutes breathing rate is “20.” 20 what? Is that ppm (parts per million)? That doesn’t make much sense, but neither does 20% in air (which would be 200,000 ppm). So, what are the units used in this study? In order to understand these numbers, we need the units used.

    John C. Ratliff, CSP(Retired), CIH(2006-2017), MSPHp

    • John,

      Here is some other detail. The two standards considered are:

      EN250:2014 Respiratory protective devices – Open-circuit self-contained compressed air breathing apparatus
      This norm has a section on inspired carbon dioxide. In particular, it specifies that if a “facepiece” has an internal volume greater than 200ml, it should be tested for inspired carbon dioxide levels. Specifically:
      – 10 l/min (10 breaths per minute of 1 liter each): the carbon dioxide level should not exceed 20mbar
      – 62.5 l/min (25 breaths per minute of 2.5 l each): the carbon dioxide level should not
      exceed 10mbar

      EN14143: Respiratory equipment – Self-contained re-breathing diving apparatus
      This norm deals extensively with carbon dioxide since it covers equipment meant to recirculate exhaled air by removing the exhaled carbon dioxide. The only part relating to a snorkeling full face mask is section where it is stated that the volume-weighted average inspired partial pressure of carbon dioxide during each inhalation shall not exceed 20mbar.

      Finally, the units of the tests are in mbar.

  2. I live in UK and use a Tribord (Decathlon) snorkel mask. They are readily available in the UK for about £30, bearing in mind the makers are only based in France. I had a problem breathing properly while swimming (I’m 67 and have had a stroke) and found using the Tribord tamed my breathing. In fact my local authority will not allow conventional mask and snorkel in any of our three municipal pools but four of us are allowed to swim with the Tribord. Do you have the CO2 figures for the genuine Tribord mask?
    I use mine for pool swimming because using the snorkel mask means I don’t have to synchronise my breathing with my stroke – I just breathe normally through my nose.
    Would the problem be partially down to tourists renting a snorkel mask without any instruction? They need to know how to use the mask safely – I taught myself in the warm environment of a heated lifeguarded swimming pool. It took me about a week to get used to my mask. The warm seas around Hawaii could tempt people to try using a snorkel mask without knowing how to use it safely. The problem doesn’t really occur much in the UK because the cold, murky seas surrounding our coasts are a bit of a disincentive. I tried mine in the sea which was so murky I could barely see further than my hand.

    • Peter,
      I can’t prove it, but my best guess is that the Tribord from Decathlon is the 2nd in the comparative table.
      The ID letter is “D” and it’s described as “branded competetive product”.
      D like Decathlon ?

  3. I almost died in one of these mask on 2/25/18 in Hawaii. It was my first time using one of these masks. I spent 2 days in a hospital on my vacation. I snorkel often and I swim often. I’m not a dive expert but I am an ER nurse and knew I was retaining CO2. It was the sequelae that almost killed me. Trying to swim back to shore, control you breathing was nothing short of a miracle for me. I will never use this mask again and recommend others don’t either.

    • Judy, I am so sorry to hear about your incident, glad to hear you made it. My partner drown snorkeling in Maui in January, he was wearing a full face mask (I had one as well and did not like it). His death was classified as a drowning but I have to think the mask could have been the cause.

  4. Dear Judy and Heidi, I m sorry to read what happened to you. Could you please tell me which Mask Models (Name/Brand) were used? As well I would like to know from you Judy how you were breathing when you struggled. Was it kind of a “hyper ventilation” where you breathed out more heavily than your breathed in or was you very relaxed with a calm in and out breathing?

  5. As a former anaesthetist, I wonder how much dead space there is in a full face mask ? I have only snorkelled with a conventional half mask and a separate snorkel. If I had to use a full face mask, I expect would try to increase my tidal volume, that is take deep breaths. If I took normal breaths, rebreathing might cause hypoxia as well as hypercapnia.


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