Accessory device for safety breathing equipment

An accessory device for safety breathing equipment which comprises a generally triangular bag of impervious flexible material tapering downwardly from a wide closed top at which a handle is provided, the bag having a zip-type fastener by which the filter unit of a respirator can be loosely accommodated and supported in a voluminous upper region of the bag equipped with an inlet valve, with a hose which couples to the face mask projecting from the narrow bottom of the bag which tightly surrounds said hose when the bag is closed around the filter unit by means of the zip-type fastener.

FIELD OF THE INVENTION 
This invention relates to an accessory device for safety breathing 
equipment. 
BACKGROUND TO THE INVENTION 
When work is being carried out in a toxic atmosphere, for example an 
atmosphere which is potentially dangerous due to the presence of poisonous 
gases or fumes, radioactive dust, asbestos dust or the like, it is 
conventional practice for personnel entering the dangerous environment to 
put on a respirator in the form of a face mask fed with clean air through 
a hose or hoses connected to an air filter unit which is also worn, for 
example by attachment to a waist belt. On entering and leaving the 
dangerous area, personnel pass through successive decontamination zones, 
typically including a cubicle for changing into or out of a transit suit, 
when leaving on the way to a final decontamination zone at which the 
respirator is removed, showering is carried out, and a further change of 
clothes is made. Air pumps or air movers are employed to establish a 
pressure gradient decreasing from downstream to the upstream working area, 
to assist confinement of contaminant material to the dangerous area being 
worked. One problem which arises at the showering stage is that, although 
the face mask would in theory preferably be left on during initial 
washing, or possibly removed and separately washed, the filter unit has to 
be kept dry to avoid clogging of the filter and other possible damage. On 
the other hand, the contaminated filter unit should not be exposed to the 
clean environment on the far side of the shower cubicle from the dangerous 
area. In practice, therefore, the respirator is often removed before 
entering the shower cubicle, and left there in dirty condition for 
subsequent use. However, this act of removing the face mask outside the 
shower can cause scattering of dangerous dust and particulates in an area 
downstream of the primary decontamination zones. 
Other problems can also arise in connection with the theoretically 
preferred practice of not removing the respirator prior to showering, 
which is an important requirement not only for safety of the personnel 
involved, but also for the general purpose of confining contaminant 
material. 
Moreover, further problems can arise in handling the respirator with an 
unclean filter unit downstream of the shower cubicle, i.e. in the 
nominally clean environment, particularly in view of the fact firstly that 
the filter unit usually operates from a rechargeable power supply, and 
recharging may be required prior to future use, and secondly that the used 
filter elements may have to be replaced by fresh ones. 
It is an object of this invention to provide a solution to the 
above-described problem. 
BRIEF SUMMARY OF THE INVENTION 
According to the invention, there is provided an accessory device for 
safety breathing equipment, comprising a bag of flexible impervious 
material, narrowing from a wide closed top to a relatively narrow bottom 
end, said bag having means at the top by which it can be carried, a 
voluminous region below the top for accommodating the air filter unit of a 
respirator, a region of reducing width below said voluminous region for 
accommodating the hose or hoses leading towards the face mask of the 
respirator, and a means of closure extending from the bottom end to a 
point at or adjacent the closed top and which, when the bag is in use, 
closes the bag tightly around the hose or hoses extending out of its 
bottom end and loosely encloses the filter unit in the voluminous region, 
the arrangement also providing for air access to the interior of the bag 
for enabling continued operation of the filter unit when required. 
One convenient form of closure means may be a zip-type fastener. Since 
while any dangerous dust is present the respirator can be kept 
operational, a small negative pressure will exist inside the bag 
sufficient for preventing contaminant material from exiting through the 
closure, which may nevertheless permit entry of air for operation of the 
filter unit. Alternatively, a zip-type closure which effects a seal may be 
employed, in which case an air entry valve to the bag interior may be 
incorporated. This valve may be provided in the carrier means, e.g. 
handle, at the top, the air entry to such an air inlet valve then 
preferably facing downwardly. In a preferred embodiment, however, an air 
inlet valve (one-way valve) is provided in the wall of the bag at the 
voluminous region thereof, the body of said valve being shaped and 
dimensioned to serve as a spacer which prevents the bag material from 
being sucked towards the intake of the operational filter unit. It would 
alternatively be possible to incorporate the air inlet valve and the 
spacer as separate components. 
A suitable material for the bag is an impervious plastics material, for 
example sheet polyethylene. The bag material may be semi-transparent to 
facilitate operation of an enclosed filter unit switch. 
In the preferred embodiment the bag is generally triangular in shape if 
flattened, with a straight zip-type fastener adjacent one inclined side 
edge or on the vertical bisector of one triangular face. The bag is 
preferably rigidified along its top edge, as by incorporation of a 
stiffening rod, so as better to retain its shape when being carried from 
the top with the filter unit supported inside it, at the level below which 
it is unable to drop further owing to the reducing cross-sectional area of 
the bag towards the bottom end at which the face mask hose or hoses exit 
from said bag. 
The bag may be provided with one or more external flaps; one such flap may 
serve to cover the zip-type fastener to prevent entry of water and another 
may protect the intake to the air inlet valve against entry of water. 
Alternatively, an externally louvred air inlet valve can serve to prevent 
entry of water. 
In addition to an air inlet valve, if required, the bag may also 
incorporate an access point for enabling recharging of the power supply of 
a filter unit housed in the bag. 
In another possible arrangement, to assist in ensuring that the filter 
unit, when operating within the bag, is not choked by drawing the material 
of the bag on to the filter intake, the bag may also incorporate a support 
means at or adjacent the bottom of the voluminous region, said support 
means in use supporting the filter unit so that the weight of the latter 
does not stretch the bag material in the voluminous region in which said 
filter unit is accommodated. 
USE OF THE INVENTION 
The manner of use of the above-described filter unit protection bag will in 
general be as follows. When personnel leave the dangerous environment, 
work clothing is removed, except for the respirator, and is vacuum and/or 
otherwise cleaned as far as possible. The still operating filter unit is 
then put into the bag, which is zipped up. Leaving the work clothes 
behind, the user now goes downstream to the shower cubicle. This may 
involve passage through a transit area which is intended to be kept clean 
and may be a public area, in which case the personnel may first enter a 
zone in which a transit suit is put on and also in which the hair may be 
damped down to minimise scattering of contaminant material. As the 
operational respirator is kept on and the dirty filter unit is confined in 
the bag, the user may go downstream to the shower cubicle with minimised 
risk of scattering dangerous dust, even if passing through a nominally 
clean transit area. In this connection, it will be appreciated that the 
continued operation of the respirator causes the maintenance of a small 
underpressure within the bag, which assists in confining contaminating 
dust and the like to its interior. Just prior to the shower, the user 
removes the transit suit (if worn) and enters the shower with the 
respirator still operational and the filter unit still confined within the 
closed bag. Initial showering is performed to wash away contaminant 
material from the hair, hands etc., with the filter unit in the bag 
protected from damage by water. When the user is as clean as practicable, 
the respirator is removed, the face mask separately cleaned if necessary, 
and showering is completed. The user then passes downstream of the shower 
cubicle to put on normal clothing. The respirator, including the protected 
filter unit, is also taken downstream of the shower and the closed bag is 
left in place until the respirator is subsequently used. The respirator 
can be switched off without opening the bag, this being readily enabled by 
the flexible and generally transparent nature of the material of which the 
bag is made. The respirator is now safely transportable to a site at which 
the power supply is recharged and/or the filter elements are changed. It 
is possible, if desired, to provide the filter unit with a short extension 
lead having its end exiting and exposed just beneath the bottom of the 
bag, so that re-charging can be carried out also without removing the 
filter unit from the bag. As there is no cause not to take the respirator 
into the shower cubicle (as the filter unit is protected against water), 
there is equally no reason to remove the respirator upstream of the shower 
cubicle, for example to pass through a public transit area, which is known 
to create a health hazard.

DESCRIPTION OF EMBODIMENT 
The illustrated bag is of impervious flexible material such as relatively 
stiff semi-transparent sheet polythene. It is generally triangular in 
shape when flattened, and has a wide closed top 10, reinforced by a 
stiffening rod 11. It is provided with an integral handle 12. Below the 
top, the bag has a narrowing voluminous region 14, below which the bag 
further reduces in width to a narrow bottom end 16. A zip-type closure 18 
extends from the bottom end to the closed top adjacent one inclined side 
edge of the triangle. 
In a modification, the bottom of the voluminous region may narrow sharply 
to the top of the region of reducing width beneath it, thus tending to 
support a filter unit of a respirator without substantially stretching the 
bag material vertically in said voluminous region. It is alternatively 
possible to equip the interior of the bag with supporting lugs or the like 
for a filter unit. In the illustrated embodiment of triangular bag 
however, the reinforcement 11 along the top edge, where the handle 12 is 
provided, enables the bag substantially to retain its shape when the bag 
is being carried with a filter unit supported inside it. 
The region 14 of the bag incorporates an air inlet valve 26 (one-way 
diaphragm valve) which, in addition to providing for ready access of air 
to the interior of the bag, serves the further purpose, assuming the 
filter unit to have been correctly inserted, of spacing the bag material 
from the filter unit intake. Externally, the intake to the valve 26 is 
protected by a flap or pocket 28 which prevents water entry through said 
valve. A side flap 29 serves to shield the zip-type fastener 18 for the 
same purpose. Clearly, it would be possible to provide the bag with an air 
intake valve separate from a spacer. 
Referring to the drawing figures, particularly, FIG. 3, valve 26 includes 
an apertured rimmed front plate which is connected to an apertured rimmed 
back plate to form a shallow chamber in between in which is housed a disc 
or membrane which curved so as to bias it against an internal peripheral 
seat, thereby keeping the valve closed. 
FIG. 3 further shows valve 26 as being located in the wall of the bag 
beneath the protective flap or pocket 28 (see, FIG. 1). If filter unit 24 
is put inside the bag with its inlet against the rear face of the valve on 
the interior of the bag, then this will prevent the bag material from 
being sucked against filter unit 24 to block it. It is simply a case of 
positioning filter unit 24 correctly when it is placed into the bag. 
When the bag is zipped closed around a filter unit 24, as shown in FIG. 3, 
it closes tightly around the respirator hose 30 at its bottom end, whilst 
loosely enclosing the filter unit 24 to enable the latter to continue to 
operate. 
The illustrated bag is by way of example only and may be modified in 
various ways within the scope of the invention defined in the appended 
claims.