Travellers on commercial aircraft commonly complain, among other things, of dry air, or low humidity.

It is well known that the low humidity on board commercial aircraft affects health and comfort It affects health because the Mucociliary Clearance System (the natural defence system of mucus in our noses and throats) dries up and becomes less effective at low humidity. This makes passengers more susceptible to infection during flight It affects comfort because passengers' lips, eyes, skin and throats become dry and uncomfortable, a state of affairs implicitly acknowledged by airlines providing passengers with lip salve, moisturizer etc..

Summary of the invention

According to an aspect of the present invention there is provided aircraft headgear for a passenger, comprising: an outer fabric constructed of breathable material that can maintain an internal volume of air having a higher humidity than that of the surrounding environment in the aircraft cabin; an opening into which a user can insert their head, and which can be closed around the user’s neck; and a structural support configured to space the outer fabric from a user's face in order to create a breathing space.

In this way, the headgear can be worn comfortably by a user, without interfering with their breathing and without the outer fabric touching their face. The opening can allow the user to place the headgear on their head. The opening can be closed in order to help maintain the higher internal humidity, which permits breathing without drying the user's airways.

Preferably the opening is expandable, and is biased to a shape that closes around the user's neck. In one arrangement the opening may be elasticated. In another arrangement the opening may be closable with a drawstring.

The structural support may include a first ring that surrounds the user's head, in use, and which spaces the fabric away from the user's face. The headgear may further include a mounting for the user's crown, which positions the headgear on the user’s head.

The mounting comprises a second ring. The second ring preferably has a smaller diameter than the first ring.

The outer fabric is preferably selected to maintain the internal volume of air with a relative humidity of 30-50%, and preferably 35-45%.

The outer fabric is preferably optically opaque. In this way the user can wear the headgear for sleeping without the need for an eye mask. According to another aspect of the invention there is provided a method of constructing aircraft headgear for a passenger, comprising the steps of: providing an outer fabric constructed of breathable material that can maintain an internal volume of air having a higher humidity than that of the surrounding environment in the aircraft cabin; providing an opening into which a user can insert their head, and which can be closed around the user's neck; and creating a breathing space by including a structural support configured to space the outer fabric from a user's face when the user is lying down.

According to yet another aspect of the invention there is provided a method of maintaining a relative humidity of 30-50%, and preferably 35-45%, around the head of an aeroplane passenger, comprising the steps of: enclosing the passenger’s head with an outer fabric constructed of breathable material that can maintain an internal volume of air having a higher humidity than that of the surrounding environment in the aircraft cabin; securing an opening in the outer fabric around the user’s neck; and spacing the outer fabric away from the user’s face using a structural support in order to create a breathing space.

In this way it is possible to enclose the space around a person’s head in order to capture the humidity naturally present in a person's exhalation and to maintain the atmosphere immediately around the person's head at the optimal relative humidity for the functioning of the Mucociliary Clearance System, for sleeping and for general comfort in order to mitigate the problems caused by the low humidity of the aircraft cabin. A hood-like device made from an appropriately breathable material is appropriate to achieve this. It has been found that the maintenance of an appropriate humidity level around a passengers’ head contributes significantly to a better sleep and a more pleasant flying experience, with fewer of the respiratory and visual symptoms listed below, and reduced risk of post-flight illness.

Description of the invention

The invention is the provision of a device to capture the humidity naturally present in a person’s exhalation to increase the relative humidity and to maintain it at an optimal 30-50% relative humidity or more optimal 35-45% relative humidity around the user's face and in particular around the wearer's eyes, mouth and nose in order to:

1) improve the functioning of the user's Mucociliary Clearance System as compared to when the user is not wearing the device; and

2) reduce respiratory and visual symptoms connected to the air dryness such as eye irritation, blurred vision, sinus congestion, nose irritation, sore throat, cough and hoarseness, and consequently to assist the user to sleep for longer and more comfortably with less risk of infection due both to the proper functioning of the Mucociliary Clearance System and also to the exclusion of microbes circulating in the air outside the device. An embodiment of the invention consists of a device approximately similar in appearance to a beekeepers hat but differing crucial aspects. Beekeeping hats are usually designed as a broad rimmed hat with a mesh hanging from the rim. The mesh is designed to hang off the broad rim and away from the face, in order to keep bees away from the face, while the user is standing, crouching or otherwise vertical. This typical beekeepers hat design would not achieve an object of the invention of maintaining the breathing space 5 when the user is lying down because the fabric would fall and lie close to the user’s face when the user is lying down. Furthermore, the typical beekeepers hat design would not achieve an object of the invention because it is made of optically transparent material and would not obviate the need for an eye mask when the user is sleeping. Furthermore, the typical beekeepers hat would not achieve the objective of 30 to 50%, preferably 35-45%, relative humidity within its cavity when being worn in an aeroplane at cruising altitude because the mesh would be too permeable to water vapour. Furthermore, the typical beekeepers hat would not achieve the objective of having an adjustable opening, because it is designed to be closed to exclude bees from the internal cavity.

The relative humidity inside the cavity of the device will vary depending on a number of factors including:

1) the water vapour permeability of the fabric. The more permeable the fabric, the more water vapour will pass through it and the lower the humidity will be in the internal cavity.

2) the volume of the internal cavity. The greater the internal volume of the cavity, the more water vapour will be required to achieve a given humidity.

3) the external humidity. The lower the external humidity, the greater the gradient of humidity on either side of the water permeable fabric and the faster water vapour will pass through the fabric.

4) the external and internal temperatures. Water vapour transmission through breathable fabrics depends on the temperature gradient The relationship between evaporation rate at 40 C and 80 C is linear but at lower ambient temperatures, condensation may form on the inner surface of breathable fabrics, adding an extra barrier to water vapour transfer.

(https://www.researchgate.net/publication/249776840 A Review on Designin g the Waterproof Breathable Fabrics Part Construction and Suitability of Br eathable Fabrics for Different Uses

5) the tightness or looseness of the seal around the user’s neck. The looser the seal around the wearer’s neck (or any other aperture through the fabric) the more water vapour will be lost through it and the lower the humidity inside the cavity.

The external humidity will change during the flight according to the altitude at which the aeroplane is flying, because the air circulating in the aeroplane is drawn from outside the aeroplane. The higher the altitude, the less humid the air and so it is expected that the relative humidity inside the aeroplane cabin will drop and rise according to the relative humidity outside the aeroplane.

A prototype embodiment device has been created and tested. A digital hygrometer (https://www.brannan.co.uk/digitaI-indoor-outdoor-thermomete r- and-hvgrometer) accurate to 1% relative humidity was used to test the device.

In conditions in which the ambient relative humidity was 11%, the relative humidity in the cavity of the tested device was 43-45%. The ambient temperature was 22 degrees while the temperature in the cavity of the tested device was 29 degrees.

The outer fabric that is used in the construction of the device was tested for water vapour permeability under standard BS7209:1990 (the Evaporative Dish Method) and was found to have water vapour permeability of 681.7 g/m ² /day giving a Water Vapour Permeability Index (WVPI) of 106%. By comparison, Wilbik-Haigas et al found in Air and Water Vapour Permeability in Double- Layered Knitted Fabrics with Different Raw Materials (FIBRES & TEXTILES in Eastern Europe July / September 2006, Vol. 14, No. 3 (57) available at http://www.fibtex.lodz.pl/pliki/Fibtex (ky09vb0dsw5knul5).pdfl that the double-knitted fabrics they tested had water vapour permeability under standard BS7209:1990 in the range 650-900g/m ² /day. A standard cotton/polyester mix fabric would have water vapour permeability of around 900 - 1000g/m ² /day. A typical waterproof breathable fabric should have a minimum 80% WVPI.

There are many different laboratory-based tests for breathability. In the Evaporative Dish Method (British Standard 7209 1990) a specified amount of water is placed in a dish which is then covered with the fabric being tested and sealed. The sealed unit is then weighed. The dish is then placed on a turntable in a conditioned environment, the conditions being 20 ^S C ± 2 ^Q C 65% Relative Humidity ± 4%, which rotates at 2 revolutions per minute. As the dishes rotate it is causing a small current of air in which the water inside the sealed unit tries to pass through the fabric under test. The basic principle is to determine how much of the water contained in the sealed unit will permeate through the fabric. At the same time a control sample is tested with a fabric of a known permeability range. After a specified length of time (up to 24 hours) the dishes are reweighed and the index is calculated as a percentage weight loss against the weight loss of the control sample. The higher the percentage index the more permeable the fabric is. It shows a good correlation with field trials.

The internal volume of the prototype embodiment device is approximately 9150cm3.

Various modifications could be made to the device, including without limitation a built in neck support pillows (of the design commonly seen on sale in airports and other retail outlets), or ear defenders/ear plugs attached to the device. The device can be made of fabric impermeable to light so that the wearer need not wear an eye mask. The device is primarily designed for use while sleeping but could also incorporate a design or be made of a fabric which would enable the wearer to use it while, for example, watching a movie or reading a book.

Figure 1 shows a side profile of an embodiment of the device with:

- Outer fabric 4 selected to have the properties outlined above, specifically to achieve a relative humidity of 30-50%, and preferably 35-45%, around the head of an aeroplane passenger. As explained above, a number of factors may in combination affect the relative humidity around the head of the aeroplane passenger in use, and these factors are balanced to achieve the desired relative humidity, in use.

- Opening 3 which could be elasticated or using a drawstring to close loosely or snugly around the wearer's neck. Incorporating an adjustable opening enables the user to enlarge or restrict the size of the gap between the seal and the user's neck, thereby adjusting the humidity inside the cavity to the user’s preference by permitting greater or lesser flow of air into and out of the internal cavity

- Structural ring 2 to hold the device on the top of the wearer's head. Structural ring 2 helps to fix the device in position on the user’s head in particular while the user is sitting up. It is important for the device to remain in position so that the breathing room 5 can be maintained by structural ring 1 being positioned correctly.

- Structural ring 1 to hold the fabric away from the wearer's face to create breathing room 5. In the prototype structural ring 1 was sewn into the fabric at a distance from and in the appropriate plane in relation to structural ring 2 so as to lie on a horizontal plane at approximately the same height as the tip of the user's nose when the user is in a sitting position, so as to achieve breathing space 5 and maximise the user's comfort in keeping the fabric away from the user's skin. When the user lies down with their head resting sideways (i.e. cheek down) or with their head resting on its back the structural ring 1 is held in the vertical plane by the fabric and creates a tent-like structure which maintains the breathing space 5.

- Structural rings 1 and 2 of the prototype were made out of metal wire and were sewn into a fold in the fabric. The rings could be made instead from fibreglass, plastic or any other material which would maintain its shape while in use. Further, the rings could be made of a material sufficiently flexible and re-formable so that the device when not in use could be folded into a smaller package, similar to a self-erecting tent The structural rings 1 and/or 2 could be glued onto the fabric or attached by other means, including by a means which would enable them to be removable when not in use.

Figure 2 shows a vertical view of an embodiment of the device with structural rings 1 and 2 and breathing space 5 enclosed by suitably water vapour permeable fabric 4. It can be seen that the structural rings 1 and 2 are aligned vertically at the rear of the device (where the back of the user's head is) so that the fabric falls directly vertical and rests against the back of the user’s head when vertical. This maximises the breathing space at the front of the device for any given fixed internal volume. The larger the breathing space and the further away the fabric is from the face, the more comfortable the user is likely to be, especially any who suffer claustrophobia. An eyelet can also be included around eye level so as to enable claustrophobia sufferers a small view out, whilst keeping in mind the humidity parameters. Figure 3 shows a side view of an embodiment with a neck cushion 6 attached at the opening 3 so as to form a single device for use in upright seating. Passengers in upright seating frequently use neck cushions to increase their comfort while sleeping, and it would be simple to incorporate the device so as to create a single device which would confer all the advantages of the device of the invention as well as the advantages of the neck cushion.

Figure 4 shows a front view of an embodiment with a drawstring 7 attached at the opening 3 so as to enable the user to adjust the size of opening 3.

Figure 5a shows a view from the underneath, showing the drawstring 7 to close the opening 3.

Figure 5b shows a view from the underneath, showing the neck cushion 6 attached at the opening 3.

Figures 6a and 6b show a view of the device constructed with only structural ring 1 and without structural ring 2.

Water vapour permeable fabric 4 could be either optically opaque or optically transparent, or combination of both. The advantage of being optically opaque is that the need to wear an eye mask to exclude the lights of the cabin when trying to sleep would be reduced, because the device would help to block light out. The figures show the image of a user's face inside the device but clearly if the device were made of optically opaque material then it would not be possible to see the user's face from the outside. This is also an advantage in terms of privacy. The advantage of it being optically transparent would be that the user could watch a movie, read a book or do anything else which requires being able to see externally while wearing the device. The water vapour permeable fabric 4 can be composed of more than one material, for example an optically opaque material and an optically transparent material. The optically transparent material can be provided in a position that enables the wearer to see out, while the optically opaque material comprises the remainder.