Excessive pressure on the tissues of the face and head
The problem of different facial physiology and the comfort of wearing a full-face mask and a respirator are very much related. Typically, respirator and full-face mask manufacturers divide 2 sizes in height from chin to nose bridge and also 2 sizes in width of facial cheekbones. As a result, 3 and rarely 4 sizes are used for the obturator. However, manufacturers do not make special sizes depending on the width, height and length of the nose, depending on the size of protruding cheekbones, depending on the size of the chin. It’s really hard to foresee everything. The anatomy of the head, facial bones and muscles is very diverse.
In order for the obturator to fit comfortably to a person’s nose, 2 factors must be responsible for this – the geometry of the curvilinear shape of the walls and folds, and the softness and elasticity of the material. For a tight fit to the chin it is necessary to correctly determine the size of the fold, the thickness of the material in this area, the size of the slit for fixation of the chin bones. For the cheekbones it is also important to choose the correct curvilinear shape and size of the fold, as well as the thickness of the material.
The obturator has a very important role. On the one hand it is important to have a tight fit and no air gaps, on the other hand the pressure on the skin and facial muscles should not be so strong as to cause circulation problems in the tissues or even worse to form hematomas due to excessive pressure over a long period of time.
However, all respirator manufacturers have only three attachment and pressure points: the contour of the obturator, the back of the head and the neck at the base of the skull. And the wrap of the head at the back is made with elastic bands not more than half an inch wide. This means that with the necessary tension of the mounting system, the pressure on the small area of tissue underneath them will be excessive. It is also important to note that other than the back of the head, these are all soft tissues and excessive pressure on them causes discomfort for most people.
The full-face masks have a small pressure area on the brow bones, thus increasing the pressure area and improving the fixation on the face. But the soft tissues at the back of the head are still affected, especially due to the particular deformation of the geometry of the elastic fixation bands, their edges dig into the skin of the scalp.
In the Furtherium mask models, we have solved these problems as follows. The obturator is not an independent design element, the pressure in the front face protrusion is also spread on the frontal bones due to the four elastic dampers that take up much of the pressure. In addition, the front part of the mask has a second insulating elastic seal around the facial oval, which also improves the fit and partially spreads the pressure from the front.
We abandoned the mounting design by means of elastic bands, even though it is cheaper. Furtherium uses a rigid folding design, the tensioning force of which is adjusted by the upper and lower rack and pinion mechanism. Supporting is done by ten elastic dampers, repeating the anatomy of the back of the head. It is not difficult to guess that with the same tensioning force, the pressure on each area of the main skull bones is several times lower compared to its analogues.
In simple words about our innovations. The pressure is exerted mainly on the brow and occipital bones of the skull, to a lesser extent on the soft tissues. When the 14 elastic dampers are deformed, no impinging sharp edges are formed, but rather a gradual transition between areas with different pressures. Significantly less pressure is spread between the seal around the face and the obturator, whose geometry is also designed for people with different physiology, such as a wide or protruding nose, protruding cheekbones, protruding chin, wide chin, or otherwise small, not strongly protruding nose, small and receding chin.
Mask visor and goggle fogging
Fogging of ophthalmic goggles inside safety glasses and visors of full-face masks is a very common problem. Part of the warm and humid exhaled air is forced into the chamber, creating condensation. The more intense the colder it is outside, and the more often the person breathes. In some full-face masks, manufacturers direct the flow of filtered air first to an isolated area around the eyes (sub- mask space), and from there the air flows through a non-return valve into the obturator and respiratory organs. The disadvantage of this scheme also has, if the seal around the face is not well fitted a sharp inhalation will be thrown into the chamber and then enter the respiratory organs part of unfiltered air. This is dangerous. It is often seen when firefighters put a balaclava under the seal, and physicians slip a headscarf under the seal.
The problem of visor fogging in Furtherium mask is solved, on the one hand, by double glass with low thermal conductivity and different thickness. The air gap and low thermal conductivity prevent the formation of a dew point on the inside of the visor and the formation of condensation at different temperatures.
The other side of this problem we solved differently than other manufacturers. The filtered air enters the obturator directly through spigots with non-return valves that connect the filter chambers to the obturator. Openings are made in these spigots through which, during inhalation phase, and following the Bernoulli effect, some air is aspirated from the insulated chamber around the eyes (sub-mask space), causing some underpressure in the chamber, but not enough to aspirate unfiltered air from outside. In the interval between breaths, the air pressure inside the chambers of the sub-mask space is equalized by the supplied filtered air from the chambers of the two filters. This way, the sub-mask space is microventilated safely and efficiently.
If preferred, the openings on the spigots are closed with plugs and the seal around the face is removed. This makes the sub-mask space uninsulated and self-ventilating, which is suitable for medical personnel working in environments with a risk of bacterial and viral infections, which are not dangerous when in contact with the mucous membranes of the eyes. The respiratory system remains isolated and protected.
There are several options for wearing the mask:
(1) Full isolation of unfiltered air access to the face and respiratory organs, the ventilation of the sub-mask space is open (the vent plug is removed – part of the air is taken in through suction from the sub-mask space).
(2) The face seal is removed, the vent plug is put on, the ventilation of the sub-mask space is natural, and unfiltered air has no access to the respiratory organs (face shield mode).
(3) Bottom part of the mask with filters removed, no air filtration (augmented reality helmet mode only).
Risk of dehydration
A person without air is capable of concentrated and efficient performance of most functions for an average of one minute. Without water, a person feels comfortable for one to three hours of passive activity and fifteen minutes to an hour of active duty. Factors that influence the need for fluids are also the ambient temperature, the possibility of evaporation from the body surface and cooling of the body, the person’s speech and the stress experienced.
In the outfitting of medical personnel, firefighters, police, special and military units, when using personal respiratory protection for several hours, a person is at risk of dehydration or risk of infection or poisoning if they decide to drink a liquid and remove their respiratory protection to do so.
We have solved this problem by embedding a standard drinking system into the mask and the obturator. Both openings can be plugged if preferred.
Most respirators and full-face masks partially transmit sound waves, distorting the voice. For use with a radio communication headset, a fairly inexpensive kit costing about $400 is used that attaches to the outside of the obturator, which is not an optimal solution.
In our design, a very small microphone is sealed into the obturator and always works. In the case of conversations with people around you, you only need to turn on the loudspeaker and there is no need to strain your vocal cords. In the case of radio or phone communications, the microphone will transmit a person’s voice very clear and precise, with almost no audible or intelligible voice from the outside. For emergency, police and military personnel, the clarity of voice messages means the accuracy of understanding by others. Very often there is no time to repeat what has been said.