The Bulletin of Kawasaki Takatsu Shinryo-jyo 1(1): 14-18, 2020

Short Note

Development of an N95 compatible full-face mask
Hideo Matsui1*, Takashi Kobayashi1

Introduction
A personal protective equipment (PPE) of level 2 (the wearing of both goggles and anN95 mask in our clinic) is necessary for the medical examination in patients with
COVID-19. However, when an N95 mask attaches to face so that there is no leak,breathing is unexpectedly hard, and the long-time work is difficult. In Japan, there isthe severe current situation that N95 masks are not available, and many hospitals
have been running short of N95 masks as well as other PPE. Therefore, as having both
function of the masks and goggles, we converted a snorkel mask (full-faced type) to an
N95 compatible full-face mask according to the procedure reported by Stanford
University Prakash Lab1).

M aterials and M ethods
1) Preparation of a full-face snorkel mask, viral filters and the 3D-printed adapter
Today, wide variety of full-face snorkel masks is commercially available. We
purchased a full-face snorkel mask (Zenoplige, China) from Amazon Japan on-line shop(Fig.1A). The original mask has a foldable snorkel pipe at the top edge of theventilation port. Air circulation inside the mask is controlled by a set of one-way valves
placed near the nosepiece, which allows one-way circulation of air. This mask features
a simple exhale valve at the mouth area, which is usually closed in the water.
Important point is that inhale and exhale pathways are separated (Fig.1B). In-line
viral filters can be adapted to mount to the 3D-printed part (Fig.1C). We used an ISOstandard 22mm OD viral filter (510-014, BSF104) because that has the same ratings as
N95 masks (Fig.1D). The computer-aided design (CAD) data of the adapter is shown inFigure 2.

1

Kawasaki Takatsu Clinic and VHC *Corresponding author: matsuihideo3@gmail.com

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The Bulletin of Kawasaki Takatsu Shinryo-jyo 1(1): 14-18, 2020

Fig. 1 A: An original full-face snorkel mask. B: Air circulation inside the mask: a blue line
indicates an inhaled flow, and orange lines indicate exhaled flows.
C: The 3D-printed adapter. D: An in-line filterFig. 2 The CAD data of the 3D-printed adapter

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The Bulletin of Kawasaki Takatsu Shinryo-jyo 1(1): 14-18, 2020

2) Assembly of the parts
We removed a snorkel pipe and attached the 3D-printed part, which has a latch sothat air-tight connection is achieved. Then, the viral filter was introduced to theopposite side of the adapter, which has two O-rings (Fig.3).

Fig. 3 Assembly of the parts: a latch is put on the 3D-printed flare-out part, connected tothe top edge of the ventilation port with the filter placed on the other side.

Result and Discussion
We developed a full-face mask with a viral filter by using a commercially available
snorkel mask (Fig.4). In this procedure, the 3D-printed part, by which a viral filter wasconnected, was essential to fulfill biological safety. To obtain clinical validation, we
have to do some tests: sealing capacity, filter performance, pressure drop, CO2
accumulation, and clinical usability1). In the clinical setting, it is also necessary toestablish a decontamination procedure such as autoclaving, bleach emmersion, andethanol immersion. The CDC recommends that a set of promising conditions forinactivation of SARS-Cov-2 on N95 mask, which include temperatures between 70-85°C,
humidities between 50-85%, and processs times of at least 60 minutes2). The moist heatdecontamination method would also be applied to the present mask without modifying
the material. We also take into account the way of communication through the mask,
especially in noisy condition, because the full-face snorkel mask can significantly
muffle the user’s voice. In order to solve this problem, a mobile application was created16The Bulletin of Kawasaki Takatsu Shinryo-jyo 1(1): 14-18, 2020

to relay audio from a Bluetooth® microphone inside the mask to the mobile phonespeeker1).
At present, the device is not approved for clinical use in Japan. However, we believethat this trial is very important during mask shortage in the era of COVID-19
pandemic.

Fig. 4 Complete of an N95 compatible full-face mask

Acknowledgem ent
We thank Yoko Matsui (MFORGE Industries) for his technical assistance, Mizuki JayMatsui (MijeLab) for providing us of graphic design.

Conflict of interest
We declare no conflict of interests for this manuscript.

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The Bulletin of Kawasaki Takatsu Shinryo-jyo 1(1): 14-18, 2020

References
1) Kroo L, et al. Pneumask: Modified full-face snorkel masks as reusable personal
protective equipment for hospital personnel. medRxiv (preprint) 2020.
doi:10.1101/2020.04.24.20078907
2) N95DECON. Technical report for heat-humidity-based N95 reuse risk management.
N95Decon research document (not-peer-reviewed). version 2.0, 4/23/2020

川崎高津診療所紀要 (The Bulletin of Kawasaki Takatsu Shinryo-jyo)
Published on line, August 12, 2020 (v2.1) and revised form, August 10, 2022 (v2.2.1)

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