AU2022263491A1

AU2022263491A1 - Apparatus for drying rooms

Info

Publication number: AU2022263491A1
Application number: AU2022263491A
Authority: AU
Inventors: Richard Ralph Halstead; Ian David Hopkin; Jonathan Jayne; Ashley Charles Norman; Pawel Tomasz Turek
Original assignee: DBK David and Baader GmbH
Current assignee: DBK David and Baader GmbH
Priority date: 2016-01-04
Filing date: 2022-11-01
Publication date: 2022-12-08
Also published as: AU2016200001A1

Abstract

OF THE DISCLOSURE A hand-portable drying apparatus and method for use in a damp or waterlogged room, the apparatus including a housing having a carrying handle, the 5 housing containing first and second airflow ducts arranged generally parallel to each other and having respective air inlet and air outlet ends, the apparatus further including means to force air through the ducts and to selectively heat it in at least one of the ducts, and valve means within the housing to selectively direct air from the first duct to the second duct whereby to move air from within the room received by 0 the first duct back to the room via the second duct or to expel air from the room via the first duct to outside the room and draw in fresh air from outside the room via the second duct.

Description

Apparatus for drying rooms

This invention relates to the general subject of water damaged rooms and

buildings as described in US patent 9015960 (the "960 patent"), the disclosure of

which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The '960 patent describes a novel method of drying a damp or waterlogged

room through the use of heated ducting which permits heated air to be recirculated

within the room until it reaches a required humidity level or until a given time period

has elapsed, whereafter the heated air is exhausted from the room via the ducting.

The apparatus for accomplishing this is shown in Figures 4 to 7 of the '960 patent

and essentially consists of a portable steel trolley supporting a housing and various

air inlet and outlet ducts, five in total, for moving heated air around the room being

dried in air recirculation mode and, in exhaust mode, removing hot and humid air

from the room, to be replaced by ambient air from outside. This arrangement has

proven to be very satisfactory in many respects but has some disadvantages,

including that the apparatus is quite bulky and therefore cannot be used in confined

spaces, such as in crawl spaces below floors or roofs. In addition, being mounted

on a trolley the apparatus is quite heavy, weighing over 50 kg and is therefore not

suitable for being lifted by a single person without risk of injury.

The present invention is derived in part from the realisation that the movement

of heated air around or from a damp room should be possible by means of apparatus

that is more user friendly than that described in the '960 patent.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a hand-portable

apparatus for drying rooms, the apparatus including a housing containing first and

second airflow ducts arranged generally parallel to each other, each airflow duct

comprising a first end connectable to an exterior of the room and a second end

connectable to an inside of the room, an electronic control unit (ECU), electric fan

means operable by the ECU to move air through the ducts, a sensor means

arranged within the ducts to sense a temperature and a humidity of air within the

room and provide signals indicative thereof to the ECU, an electric heater means

operable by the ECU and arranged to heat air being passed to the inside of the

room, and a valve means located between the first end and the second end of the

ducts, the valve means settable for (i) operating the apparatus in a first, recirculating

mode in which the first airflow duct and the second airflow duct are pneumatically

connected and air entering the apparatus from the room is recirculated into the room,

and for (ii) operating the apparatus in a second, exhaust mode in which air is passed

from the inside of the room to the exterior of the room via the first airflow duct and air

is passed from the exterior of the room to the inside of the room via the second

airflow duct, wherein the valve means is set to operate in the first recirculating mode

until a given level of humidity and/or temperature of the air in the apparatus has been

detected or a given time period has elapsed..

In some variations of the first aspect, the apparatus includes a housing having

a carrying handle, the housing containing first and second airflow ducts arranged

generally parallel to each other and having respective air inlet and air outlet ends,

the apparatus further including means to force air through the ducts and to

selectively heat it in at least one of the ducts, and valve means within the housing to

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selectively direct air from the first duct to the second duct whereby, in a first mode, to

direct air from within the room received by the second duct back into the room via

the first duct or, in a second mode, to expel air from the room via the second duct to

outside the room and draw in fresh air from outside the room via the first duct.

With this arrangement, the essentially parallel configuration of the first and

second ducts allows for the housing to be of size and shape similar to a suitcase

therefore being easily portable. Where multiple such apparatus are to be

transported, stored or even used together, each housing may include projections and

recesses by which they may be stacked together.

Conveniently, the valve means is a single butterfly valve acting between the

walls of the first and second ducts by which, when opened, air entering each duct is

free to exit unimpeded through the same duct but, when closed, air entering the

second duct is instead redirected to the first duct for recirculation into the room.

Alternatively, the valve means may comprise other types of valve means such

as a pair of flap valves, one for each duct which, when closed, together act to

circulate air initially drawn in from the room by the first duct to the second duct and

expel it back into the room, and when open act to allow the free flow of air through

the ducts in opposite directions, allowing fresh air into the room via the first duct and

previously recirculated air to be expelled via the second duct.

The housing is conveniently in the form of a suitcase, being of moulded

plastics and having a carrying handle, the housing having first and second air flow

ducts which each include an electrically driven fan, downstream of at least one of

which is an electrically operable heater whereby to selectively introduce heated air

into the room being dried, the ducts being pneumatically separated by the valve

means, the valve means being operable when closed to redirect air received by the

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second duct to the first duct and back into the room.

Where the valve means is a single butterfly valve acting between the first and

second ducts, each such duct may conveniently be curved towards the other in that

region so that when the butterfly valve is closed air entering the second duct is

smoothly redirected to the first duct in the opposite direction, for recirculation into the

room. To compensate for any restriction to the air flow caused by the curvature of

the ducts when the butterfly valve is open, the height of the ducts in this region is

preferably raised relative to the height of the ducts elsewhere.

Where the valve means comprises a pair of flap valves, one for each duct,

they may conveniently be arranged such that, when closed to prevent ingress or

egress of air to ambient, they define a substantially "V" shaped configuration

whereby to redirect air moving through the second duct in one direction to the first

duct in the other direction and back into the room. The aerodynamic efficiency when

the valve is closed may be improved by at least one of the flap valves being curved

and being receivable when not in use within a correspondingly shaped recess in the

housing.

In some variations of the first aspect, the electric fan means comprises a first

fan and a second fan, configured such that, in the second exhaust mode, the first fan

causes air to be passed through the first airflow duct and the second fan causes air

to be passed through the second airflow duct. The apparatus further comprises

means to adjust the speed of the first and/or second fan to vary an airflow over the

heater means, such that the temperature within the room is varied.

In some variations of the first aspect, the apparatus further comprises a

second valve means which prevents ambient air from entering the room via the

second airflow duct of the apparatus when the fan means is operating to exhaust air from the room via the first airflow duct so that a negative pressure occurs in the room.

Also disclosed herein is a method of drying a room using the apparatus of the

first aspect. The method includes the steps of providing heater means, a first airflow

duct and a second airflow duct and associated first and second airflow fan means

for, in the second exhaust mode, passing air from the inside of the room to the

exterior of the room via the first airflow duct and passing air from the exterior of the

room to the inside of the room via the second airflow duct, and, in the first

recirculating mode, recirculating heated air within the room while substantially

preventing ingress or egress of air into or from the room, sensing the temperature

and/or relative humidity within the room, and adjusting the airflow of the first and/or

second fan means in response to an indication that a required parameter has not

been reached or has been exceeded when the apparatus is operating in the first

recirculating mode.

Also disclosed herein is a method of drying a room using the apparatus of

some variations of the first aspect in which the apparatus further comprises the

second valve means. The method includes the steps of operating the apparatus in

the first recirculating mode in which heated air is recirculated within the room,

operating the apparatus in the second exhaust mode in which air from the inside of

the room is exchanged with ambient air from the exterior of the room until the relative

humidity of the air from inside the room generally corresponds to ambient air

humidity, operating the apparatus in a third negative pressure mode in which further

ambient air is prevented from entering the room while air continues to be passed

from inside the room to the exterior of the room, to thereby provide negative air

pressure in the room, encouraging evaporation from damp surfaces.

According to a second aspect of the invention there is provided an apparatus

for drying a room, comprising first and second airflow ducts within a housing, the

ducts being switchable by valve means for, in a first mode, for introducing fresh air

via the second airflow duct from outside without the room being dried and exhausting

air via the first airflow duct from within the room via first and second fan means and,

in a second mode, closing the valve means to thereafter recirculate air within the

room by directing air from the first airflow duct to the second airflow duct and moving

air from within the room received by the first duct back to the room via the second

duct until a given level of humidity has been reached or a given time period has

elapsed, and electric heater means downstream of the first fan means for selectively

heating the air in the room, the apparatus further including means to adjust the

speed of the first and/or second fan means to vary the airflow over the heater means

to thereby increase the temperature within the room as required.

The present disclosure in a second aspect is derived from the further

realisation that the method described in the '960 patent can be improved in

circumstances where it is difficult or impossible to achieve a required temperature of

the air within a room being dried due to e.g. the availability only of a low level of

electrical power, such as domestic electrical power, or due to the large size of the

room being dried.

In some variations of the second aspect, the apparatus for drying a room

comprises first and second airflow ducts within a housing, the ducts being switchable

by valve means for, in a first mode, closing the valve means to thereafter recirculate

air within the room until a given level of humidity has been reached or a given time

period has elapsed, and, in a second mode, introducing fresh air from without the

room being dried and exhausting air from within the room via first and second fan means, and electric heater means downstream of the first fan means for selectively heating the air in the room, the apparatus further including means to adjust the speed of the first and/or second fan means to control thermal losses from the room.

Also disclosed herein, which is applicable to any type of domestically powered

room drying apparatus, there is provided a method of drying a room including the

steps of providing heater means and first and second airflow ducting and associated

first and second airflow fan means, and in a first mode, selectively recirculating

heated air within the room while substantially preventing ingress or egress of air into

or from the room, and in a second mode for selectively introducing fresh air from

without the room being dried and exhausting heated air from within the room being

dried, sensing the temperature and/or relative humidity within the room, and

adjusting the airflow of the first and/or second fan means in response to an indication

that a required parameter has not been reached or has been exceeded when the

apparatus is operating in the first mode.

In a further refinement, the apparatus and method may include valve means

which prevents ambient air from entering the room via the apparatus when the

exhaust fan is operating so that a negative pressure occurs in the room when the

apparatus is operating in this mode. This is particularly useful when measurement

of the relative humidity of the air within the room indicates that it is no longer

saturated, the negative pressure thereby encouraging the construction materials

within the room to give up their water content by increased evaporation. By way of

example, the negative pressure valve means may be incorporated within the

apparatus or may be provided separately where, in each case, the valve means is

only operated to provide negative pressure in the room towards the end of each air

recirculation cycle when the relative humidity remains substantially constant or when, after a succession of drying cycles, the relative humidity of air within the room is remaining substantially constant, indicating that the air is in an unsaturated state but that some or all of the room construction materials are still wet or damp.

According to a third aspect of the invention there is provided a room drying

apparatus which includes fan means and associated ducting for introducing ambient

air into the room via a second duct, recirculating it within the room by directing air

from a first duct to the second duct and moving air from within the room received by

the first duct back to the room via the second duct and sequentially exhausting the

recirculated air from the room via the first duct after a sensed condition of air within

the room has been reached, the apparatus further comprising valve means which

prevents ambient air from entering the room via the second duct of the apparatus

when the fan means is operating to exhaust air from the room via the first duct so

that a negative pressure occurs in the room.

Also disclosed herein is a method of drying a sealed room using the

apparatus of the third aspect of the invention. The method includes the steps of

sequentially recirculating heated air within the room and exchanging it with ambient

air from without the room until the relative humidity of the air generally corresponds

to ambient air humidity, and thereafter preventing further ambient air from entering

the room while continuing to exhaust air from within the room to thereby provide

negative air pressure in the room encouraging evaporation from damp surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, with reference

to the accompanying drawings in which:

Figure 1 shows a top view of a hand portable drying apparatus (1) comprising a plastics housing (2) connected at each end to flexible ducts D1, D2, D3 & D4, only part of which are shown,

Figure 2 is an exposed plan view of a first embodiment of the invention in

ambient air inlet and exhaust mode,

Figure 3 is a perspective view of Figure 2

Figure 4 is an exposed plan of the embodiment of Figure 2 in air recirculation

mode,

Figure 5 is a perspective view of Figure 4,

Figure 6 is a schematic view of a second embodiment of the invention in

which a pair of flap valves are used to control air recirculation and air exhaust from

the room being dried,

Figure 7 is a schematic plan view of drying apparatus installed within a room

and operating in a first mode, and

Figure 8 is a schematic plan view of drying apparatus installed within a room

and operating in a second mode.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 shows a top plan view of drying apparatus (1) according to the

invention comprising a lightweight plastics housing (2) from each end of which

extend flexible ducts D1, D2, D3 & D4, in each case only part of which is shown.

Duct D1 is used to introduce air from outside the room being dried, the room itself

being pneumatically sealed to avoid accidental ingress or egress of air into or from

the room. Duct D2 is used to direct air that has passed through the housing (2) into

the room being dried or particular parts of the room being dried. Duct D3

reintroduces air from within the room into the housing (2) and duct D4 exhausts air

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from the room when required.

Figure 2 shows an exposed view of the housing 2 which has a first duct (3)

and a second duct (4), each connectable to the flexible ducting of Figure 1 by which

to exchange air from within a sealed room to without the room, such as to ambient

air. This is achieved by means of an air inlet fan (5) and an air exhaust fan (6).

Downstream of the inlet fan (5) is a heater (7) for selectively heating, as required, air

being drawn into the room.

A butterfly valve (8) pneumatically divides the first and second ducts (3, 4)

and in the open position shown allows generally unimpeded flow of air coming into

the first duct (3), entering the room being dried, and exiting from the second duct (4).

Figures 4 & 5 show an arrangement in which the butterfly valve (8) has been

closed such that air entering the second duct (4) from within the room being dried is

thereafter redirected by curved surfaces (9,10) from the second duct (4) to that part

of the first duct (3) immediately upstream of the fan (5), whereafter it may be

selectively heated or re-heated as required until humidity within the room has

reached a required parameter or a given time period has elapsed, whereafter the

butterfly valve (8) returns to the condition shown in Figure 2 for the purposes of

exhausting the air from within the room and introducing fresh air from without the

room. In order to compensate for the more restricted air flow caused by the curved

surfaces (9, 10) the height of the ducts (3, 4) is raised in this region.

In the alternative embodiment shown in Figure 6 the housing (2a) is shown

connected to flexible ducting (13) by which air can be moved between a room being

dried (14) and the outside of the room (15). The valve means within the housing (2a)

to selectively direct air from the first duct (3) to the second duct (4) comprises in this

case a pair of pivotable flaps (11,12) connected together for synchronous movement by a parallelogram linkage (not shown) which, when moved to the positions shown in broken lines, co-operate to form a generally "V" shaped baffle by which to redirect air entering the second duct (4) to the first duct (3) immediately downstream of the fan

(6) and upstream of the fan (5). Hence, when the flaps (11,12) are in the open

position shown they allow unimpeded flow of ambient air into the first duct (3) and

out of the second duct (4) to ambient but, when closed, they prevent air that has

entered the second duct (4) from leaving the room but instead redirect it to the first

duct (3) immediately upstream of the fan (7), thereby recirculating the air within the

room (14) until a required level of humidity has been reached or a given time period

has elapsed.

Each of the embodiments shown in Figures 1 to 5 and Figure 6 are very

compact as opposed to the apparatus shown in Figures 4 to 7 of the '960 patent and

are easily hand-portable. This is particularly convenient for using such apparatus in

confined spaces, or where there is only one operator for the apparatus, given that

there are often statutory limits to the weight which can be safely lifted by individual

employees. The simplicity of the design also lends itself to being manufactured by

plastics moulding techniques such as rotary moulding, although it will be understood

that other lightweight materials may be used instead, including aluminium. In either

case the luggage-style of the housing is convenient for both storage and transport,

particularly if the housing includes projections and recesses whereby it may be

stored into or onto corresponding projections and recesses which temporarily secure

it in place, such as into or onto a cradle for transport or stacked onto another such

drying apparatus.

Turning now to Figure 7, drying apparatus shown generally at (1a) comprises

a housing (2a) a visible display (16) in the form of a touch screen liquid crystal

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display, and an electronic control unit (ECU) (17) within the housing (2a).

Extending through the housing (2a) are first and second ducts (3a, 4a)

separated by a butterfly valve (8a) which, when in its open position shown means

that outside air can be drawn into the first duct (3a) via a first fan (5a) and expelled

from the second duct (4a) via a second fan (6a). Downstream of the first fan (5a) is

a mains-powered electric heater (7a) and further downstream is a thermostat (18) for

controlling power supply to heater (7a) on command from the ECU (17) via the touch

screen display (16).

Downstream of the second fan (6a) is a temperature and humidity sensor (19)

connected to the ECU (17).

Upstream of the first fan (5a) is a coarse filter (20) for preventing or inhibiting

the ingress of contaminants such as leaves etc into the housing (2a).

In operation in this first mode, air from within the room is constantly exhausted

from it via the duct (4a) and is constantly replenished from air outside of the room via

duct (3a). In contrast and as shown in Figure 8, in this second mode the butterfly

valve (8a) has been rotated by 90° to close off one end of the ducts (3a, 4a).

Instead, and as shown arrowed, air entering the duct (4a) through the second fan

(6a) is diverted in this mode to flow into the duct (3a) and through the first fan (5a), to

be thereafter expelled back into the room and recirculated. This recirculation allows

air within the room to become saturated by a chosen parameter which, when

reached, triggers the apparatus to switch to the exhaust mode shown in Figure 6 in

which the butterfly valve again separates the first and second ducts (3a, 4a) to allow

for the saturated air to be exhausted via the second duct (4a) and for fresh air to be

introduced via the first duct (3a).

As will be apparent, the majority of flooded rooms occur in premises where only domestic mains electricity is available, with consequent power limited to approximately 13 Amps if the supply voltage is 240 Volts. This can be problematic in cold conditions or where the room being dried is large because it limits the maximum temperature attainable within the room which, in turn, limits the rate of evaporation from saturated surfaces when air is being recirculated within the room.

Accordingly, a further aspect of the invention which is not limited to the use of

hand-portable drying apparatus but includes mains operated drying apparatus of the

type described in the '960 patent, in which the flow of air through or over the heater

means is controlled, such as by varying the speed of the or each fan to suit the

particular room being dried. Thus, reducing the speed of the or each fan not only

reduces noise within the room and noise pollution in adjacent rooms, but it also has

the effect of reducing thermal loss from the room when operating in the mode of

introducing fresh air from without the room being dried and exhausting air from within

the room via the fan means. This effectively compensates for other thermal losses

from the room, such as may be due to inadequate pneumatic sealing of the room or

due to the properties of materials within the room, such as water-impermeable stone

acting to conduct heat from the room without it heating the air, and damp mortar or

plaster. Although reducing the thermal loss in this way can be effective as compared

to a situation whereby these other thermal losses are preventing successful

completion of the drying process it will, of course, be apparent that the process itself

is necessarily extended over-time.

In a further refinement to the invention, the apparatus and method may

include negative pressure valve means which prevents ambient air from entering the

room via the apparatus when the exhaust fan is operating so that a negative

pressure occurs in the room when the apparatus is operating in this mode. This is

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particularly useful when measurement of the relative humidity of the air within the

room indicates that it is no longer saturated, the negative pressure thereby

encouraging the construction materials from which the room is made to give up their

water content by increased evaporation. By way of example, the negative pressure

valve means may be incorporated within the apparatus or may be provided

separately. In each case, the valve means is only operated to provide negative

pressure in the room towards the end of each air recirculation cycle when the relative

humidity remains substantially constant or when, after a succession of drying cycles,

the relative humidity of air within the room is remaining substantially constant,

indicating that the air is in an unsaturated state but that some or all of the

construction materials are still wet or damp.

The terms "comprising" and "comprises" are used in the present specification

to denote the presence of an integer or feature without excluding the presence of

additional integers or features. In other words, the terms are to be given their

inclusive meaning of "including" or "includes".

LIST OF REFERENCE NUMERALS

1, la hand portable drying apparatus

2, 2a housing

D1- D4 flexible ducts

3, 3a first duct

4, 4a second duct

5, 5a air inlet or first fan

6, 6a air exhaust or second fan

7, 7a heater

8, 8a butterfly valve

9, 10 curved surface

11, 12 pivotable flap

13 flexible ducting

14 room being dried

15 outside of the room

16 display

17 ECU

18 thermostat

19 sensor

20 filter

Claims

1. A hand-portable apparatus for drying rooms, the apparatus including a housing containing first and second airflow ducts arranged generally parallel to each other, each airflow duct comprising a first end connectable to an exterior of the room and a second end connectable to an inside of the room, an electronic control unit (ECU), electric fan means operable by the ECU to move air through the ducts, a sensor means arranged within the ducts to sense a temperature and a humidity of air within the room and provide signals indicative thereof to the ECU, an electric heater means operable by the ECU and arranged to heat air being passed to the inside of the room, and a valve means located between the first end and the second end of the ducts, the valve means settable for (i) operating the apparatus in a first, recirculating mode in which the first airflow duct and the second airflow duct are pneumatically connected and air entering the apparatus from the room is recirculated into the room, and for (ii) operating the apparatus in a second, exhaust mode in which air is passed from the inside of the room to the exterior of the room via the first airflow duct '0 and air is passed from the exterior of the room to the inside of the room via the second airflow duct, wherein the valve means is set to operate in the first recirculating mode until a given level of humidity and/or temperature of the air in the apparatus has been detected or a given time period has elapsed.

2. An apparatus according to Claim 1, wherein the valve means is a single butterfly valve between the first and second duct, by which when opened air entering each duct is free to exit unimpeded, but when closed, air entering the first duct is instead redirected in an opposite direction to the second duct for recirculation into the room.

3. An apparatus according to Claim 1 or 2, wherein each of the first and second ducts is curved towards the other in the region of the valve means so that when it is

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/ closed air entering one duct is smoothly redirected to the other duct in the opposite direction for recirculation into the room.

4. An apparatus according to Claim 3, wherein to compensate for any restriction to the air flow caused by the curvature of the ducts in the region of the valve means, their height is raised in this region relative to the height of the ducts elsewhere.

5. An apparatus according to claim 1, or according to claim 3 when dependent on claim 1, wherein the valve means comprises a pair of flap valves, one for each duct, which when closed act to circulate air drawn in from the room by the first duct to the second duct and expel it back into the room, and when open act to allow the free flow of air through the ducts in opposite directions.

6. An apparatus according to Claim 5, wherein the flap valves, when closed, define a substantially "V" shaped configuration thereby to redirect air moving through one duct in one direction to the other duct in the other direction.

7. An apparatus according to Claim 6, wherein at least one of the flap valves is '0 curved and receivable within a correspondingly shaped recess in the housing when not in use.

8. An apparatus according to any one of Claims 1 to 7, wherein the housing is in the form of a suitcase, being of moulded plastics and having a carrying handle.

9. An apparatus according to any one of the preceding claims, wherein the electric fan means comprises a first fan and a second fan, configured such that, in the second exhaust mode, the first fan causes air to be passed through the first airflow duct and the second fan causes air to be passed through the second airflow duct, the apparatus further comprising means to adjust the speed of the first and/or second fan to vary an airflow over the heater means, such that the temperature within the room is varied.

10. An apparatus according to any one of the preceding claims, further comprising a second valve means which prevents ambient air from entering the room via the second airflow duct of the apparatus when the fan means is operating to exhaust air from the room via the first airflow duct so that a negative pressure occurs in the room.

11. A method of drying a room using an apparatus of any one of Claims 1 to 10 including the steps of: providing heater means, a first airflow duct and a second airflow duct and associated first and second airflow fan means for, in the second exhaust mode, passing air from the inside of the room to the exterior of the room via the first airflow duct and passing air from the exterior of the room to the inside of the room via the second airflow duct, and, in the first recirculating mode, recirculating heated air within the room while substantially preventing ingress or egress of air into or from the room, sensing the temperature and/or relative humidity within the room, and adjusting the airflow of the first and/or second fan means in response to an indication that a required parameter has not been reached or has been exceeded when the apparatus is operating in the first recirculating mode.

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12. A method of drying a sealed room using the apparatus of Claim 10, including the steps of: operating the apparatus in the first recirculating mode in which heated air is recirculated within the room, operating the apparatus in the second exhaust mode in which air from the inside of the room is exchanged with ambient air from the exterior of the room until the relative humidity of the air from inside the room generally corresponds to ambient air humidity, operating the apparatus in a third negative pressure mode in which further ambient air is prevented from entering the room while air continues to be passed from inside the room to the exterior of the room, to thereby provide negative air pressure in the room, encouraging evaporation from damp surfaces.