[0001] The present invention relates to a method and a device for removing undesirable odours
from various materials, particularly smoke odour.
[0002] The common traditional method of removing undesirable odours is to ventilate the
affected object. This method is based on the fact that, in order to perceive that
a substance has an odour, it must have a certain volatility at normal temperatures
and thus be able to pass from solid or liquid form into gas form and then through
air circulation finally end up in the nose of the person sensing the smell. Solid
substances which do not have such volatility therefore do not smell.
[0003] Even if a substance has vapour pressure (which is the same as volatility), this does
not, however, mean that it will be perceived as smelling by the human sense of smell.
Pure water has high volatility but is not considered to have any smell. No explanation
has been forthcoming as to why certain substances smell and others do not despite
a measurable volatility.
[0004] The amount of a gas required to produce a smell sensation varies considerably from
one substance to another. Aceton, a common solvent, has a characteristic and rather
pleasant smell. Its threshold value, i.e. the content in the air at which the smell
is just perceivable, lies at a level of about 100 mg aceton per m
3 air. A chemically similar substance but with an entirely smell is butyric acid, having
a threshold value of 0.001 mg butyric acid gas per m
3 air. The nose is thus 100,000 times more sensitive to this gas, and no one knows
why.
[0005] One of the more common odour problems is caused by smoke. In a fire, the actual damage
from fire is often considerably less than the value of the smoke-damaged textile materials,
which in fires in carpet stores and fashion shops can reach enormous sums.
[0006] By airing and ventilation, the smell-producing substance is continually transferred
from the textile material to the surrounding air, and gradually the smell-producing
substance is completely absorbed and the smell ceases. This method, however, takes
a very long time if the threshold value for the smoke odour is very low and if the
smoke gases adhere to the textile material. Such smoke-damaged textile materials are
therefore treated with air with ozone (see DE-A-2215269), whereby the odourous substances
are oxidized to other less odouriferous compounds. It is true that this method produces
good results, but ozone is firstly a particularly toxic gas, and secondly is quite
aggressive and can easily damage colours and materials if too much is used. The present
invention constitutes a significant improvement over previous methods and will be
described in detail with reference to the accompanying drawing which shows the application
of the invention to a smoke-damaged jacket.
[0007] The smoke-damaged jacket 1 is enclosed in a sealed container 2 which can be connected
via a pipe connection 3 to a vacuum. When the box is evacuated to a pressure of several
torrs, which can be done with a simple vacuum pump, the smell-producing components
which have adhered to the outer and inner surfaces of the textile material are vapourized
to a greater or lesser degree. The vapourization takes place more quickly in a vacuum
than at atmospheric pressure since air molecules no longer obstruct or retard the
evaporation of the smell-producing components. An equilibrium is quickly achieved
between the remaining adsorbed substance and the evaporated substance.
[0008] The air which is smell-saturated, which was in the textile material surrounding its
fibers, will now expand because of the vacuum and completely fill the entire volume
of the container. Continuous pumping during this phase, with a simultaneous leeking
in of small amounts of fresh air, will remove the odourous air contained in the container.
[0009] After this step, the container is pressurized to atmospheric pressure with clean
air. This air will now be drawn even into the pores of the textile material and there
absorb additional vapourized, odouriferous material from the surfaces of the textile
fibers. By alternating in this manner between evacuation and pressurization with such
periodicity as to allow the expanding and smell- carrying air to be pumped out before
fresh air is allowed into the pores of the textile material, a stage is reached, afer
3-5 cycles, where the remaining smell-producing substance in the jacket has practically
disappeared or is in any case below the odour threshold level. A heat loop 4 can be
added in the vicinity of the textile material to accelerate the evaporation by heating.
The temperature increase is of course adapted so that the textile material is not
damaged by the heat.
[0010] A cooling loop 5 is also mounted in the container, and its surface temperature is
kept suitably at -10--20°C. Thus the evacuation can be shut off or kept at low capacity,
since the gases freed from the textile material, the odour substances, water vapour
etc., will condense on the surface of the cooling loop in accordance with the cold
wall principle. This also produces a lower pressure than what a simple vacuum pump
normally produces.
[0011] In order to prevent the textile material from coming into contact with the heat loop
or the cooling loop, bars 6 can be mounted inside the container.
[0012] The unit according to the invention can be made both for stationary and portable
use and thus can be quickly implemented for cleaning operations at out-of-the-way
locations. The only requirement is that the container must be airtight and sufficiently
strong to withstand the external air pressure when evacuated.
[0013] The method according to the invention produces a much more rapid and effective odour
removal than what was previously possible. The method has also in certain cases been
improved upon further, by using various chemicals at the same time. When removing
odours from smoke-damaged material, it is possible to add small amounts of ozone to
the air left into the container. Likewise, if there are acidic compounds, small amounts
of ammonia can be added to neutralize the odour-producing substances and thus facilitate
cleaning.
[0014] The invention has been studied experimentally with regard to the removal of aggressive
hydrochloric acid gas from textile materials. In fires with combustion of plastics
of polyvinyl chloride (PVC) type, hydrochloric acid gas is produced from the heated
plastic. This gas is eagerly absorbed on both metal surfaces and in porous material.
In order to study the effectiveness of removing hydrochloric acid from textile materials,
the following experiment was carried out.
[0015] Four balls of cotton, No. 1, 2, 3 and 4, were subjected in a glass chamber to gas
from heated PVC. No. 1 was used as a reference. No. 2 was placed in a small evacuation
chamber from which all the air was drawn out two times, and was pressurized therebetween
with fesh air. No. 3 was subjected to the same treatment as No. 2 butwith the difference
that the last pressurization was done with air in which small amounts of moist gaseous
ammonia were present. After the last pressurization, No. 3 was placed in fresh air
for a few minutes until the smell of ammonia had disappeared. Finally, No. 4 was placed
in fresh air for two hours, and a certain amount of air circulation was maintained
around the cotton. After completed exposure, each of the balls was placed in a beaker
with 100 ml of distilled water, and the chloride content and pH-value were determined
by known analytical techniques.
[0016] The following results were obtained: Mere ventilation at normal pressure (No. 4)
produced a reduction of the amount of chloride to 80% of the original value. Evacuation
and pressurization (No. 2), however, caused a reduction in residual chloride to less
than 2%. The pH-value was changed very little in No. 4 in comparison to the reference
No. 1; both values were at about 2.2. The pH-value in No. 2, however, had risen to
4.0 and in No. 3 was as high as 8.2. The total time taken for two evacuations and
two pressurizations was 10 minutes. The experiment demonstrates that the suggested
method makes it possible to, on the one hand, remove most of the odouriferous and
aggressive hydrochloric acid gas, and, on the other hand, neutralize residual acid
by chemical manipulation.
[0017] A second experiment was carried out with two balls of cotton, No. 5 and 6. A drop
of butyric acid was placed in each. No. 5 was a reference and No. 6 was moistened
with water and placed in an evacuation chamber, which was first evacuated and then
pressurized with air containing a small amount of ammonia, and after 10 minutes it
was again evacuated. A small amount of methyl iodide was then introduced into the
chamber which was left for an additional 10 minutes. The chamber was then pressurized.
Finally, the ball of cotton was left for an additional 10 minutes in fresh air and
a comparison was then made for odour intensity between the two balls. A markedly lower
odour intensity was observed in No. 6 compared with the reference.
[0018] The results are explained as follows. The major portion of the butyric acid can be
evacuated as a gaseous mixture of water and butyric acid. The remaining butyric acid
which still produces odour must, however, be removed by chemical means, in this case
by conversion, with the aid of ammonia, of butyric acid to ionogenic form, whereafter
it can be converted by methylization to a butyric acid derivative of considerably
lower odour intensity. The suggested evacuation technique in combination with pressurization
with specific chemicals thus makes it possible to eliminate difficult odour problems.
[0019] The invention has been used in practice in connection with a fire in a carpet store,
where a number of valuable carpets were smoke-damaged so as to be unsalable. Odour-cleaning
according to the invention, where the temperature of the heat loop was kept at 40°C,
and of the cooling loop at -20°C, and small amounts of ammonia gas were added, made
the carpet practically odour-free in a few hours.
[0020] In order to study the combined effect of the invention described here and conventional
ozone treatment, the following experiment was carried out. A smoke-damaged leather
coat was placed in an evacuation chamber, and the pressure was then reduced to 0.01
atmosphere. The pumping was continued for 5 minutes at this underpressure. The chamber
was then pressurized to 1 atmosphere with air containing 3 ppm (= parts per million)
of ozone. The unit was then left for 10 minutes, and evacuation was then done to 0.01
atmosphere, and was immediately thereafter pressurized with clean air without any
ozone additive. The chamber was opened and the garment was removed. All the odours
had now disappeared, both the smoke odour and the ozone odour.
[0021] What had happened was that during the first evacuation, the major portion of the
odour producing substances were able to vapourize and be pumped out from the object.
In the subsequent pressurization with ozone-containing air, the ozone was allowed
to penetrate deep into the previously air-filled pores of the leather and there exert
its oxidizing and odour-removing effect on the odour-producing substances. The subsequent
evacuation served to remove the residual amounts of the toxic ozone gas.
[0022] The entire procedure took 0.5 hours. This can be compared with 24 hours which conventional
ozone techniques usually take for the same type of object.
[0023] The smell of solvent from dry-cleaning can be removed in the same manner from textile
materials. By adding various substances producing desirable odours to the air in the
last pressurization, the material can be perfumed in various ways, e.g. plastic material
can be made to smell of leather.
1. Method of freeing sensitive material of odours, particularly removing odours from
textile materials after smoke damage from fires, characterized in that the material
is subjected to alternating vacuum and atmospheric pressure.
2. Method according to Claim 1, characterized in that the material is heated.
3. Method according to Claim 1 or 2, characterized in that the evacuation effect is
amplified by arranging a cooling loop in the vicinity of the material.
4. Method according any one of Claims 1-3, characterized in that when the material
is subjected to atmospheric pressure after evacuation, the air supply has at the same
time a chemical which is reactive with one of the odour-producing substances.
5. Device for removing odours from sensitive materials, characterized in that it consists
of an airtight container (2), in which the material is placed, means (3) for evacuating
the container, heat loops (4) for heating the air in the container, cooling loops
(5) for condensing the odour-producing substances, water vapour, etc. and possibly
one or more protective bars (6) for keeping the sensitive material in place and preventing
contact with the cooling and/or heating loops.
1. Verfahren zum Befreien von empfindlichem Material von Gerüchen, insbesondere zum
Entfernen von Gerüchen von textilen Materialien nach einer Rauchschädigung durch Brände,
dadurch gekennzeichnet, daß das Material wechselweise Vakuum und atmosphärischem Druck
ausgesetzt wird.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß das Material erwärmt wird.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Evakuierungswirkung
durch Anbringung einer Kühlschleife in der Nähe des Materials verstärkt wird.
4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß dann, wenn
das Material nach der Evakuierung atmosphärischem Druck ausgesetzt wird, die zugeführte
Luft gleichzeitig eine Chemikalie enthält, welche mit einer der geruchserzeugenden
Substanzen reaktionsfähig ist.
5. Vorrichtung zum Entfernen von Gerüchen von empfindlichen Materialien, dadurch gekennzeichnet,
daß sie aus einem luftdichten Behälter (2), in den das Material eingebracht wird,
Mitteln (3) zum Evakuieren des Behälters, Heizschleifen (4) zur Erhitzung der Luft
im Behälter, Kühlschleifen (5) zum Kondensieren der geruchserzeugenden Substanzen,
des Wasserdampfes od. dgl. und gegebenenfalls einer oder mehrerer Schutzschranken
(6) besteht, mit deren Hilfe das empfindliche Material an Ort und Stelle gehalten
und sein Kontakt mit den Kühl- und/oder Heizschleifen verhindert wird.
1. Procédé pour débarasser d'odeurs un produit sensible, particulièrement pour débarrasser
des produits textiles des odeurs de fumée résultant d'incendies, caractérisé en ce
que le produit est soumis à des alternances de vide et de pression atmosphérique.
2. Procédé selon la revendication 1, caractérisé en ce que le produit est chauffé.
3. Procédé selon la revendications 1 ou 2, caractérisé en ce que l'effet de l'évacuation
d'air est amplifié en disposant un serpentin de refroidissement au voisinage du produit.
4. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce que,
lorsque le produit est soumis à la pression atmosphérique après une évacuation d'air,
l'air qui arrive contient en même temps un produit chimique qui réagit avec l'une
des substances provoquant les odeurs.
5. Dispositif pour débarrasser d'odeurs des produits sensibles, caractérisé en ce
qu'il comporte une enceinte étanche à l'air (2) dans laquelle est placé le produit,
des moyens (3) pour évacuer l'air de l'enceinte, un serpentin chauffant (4) poùr chauffer
l'air dans l'enceinte, un serpentin de refroidissement (5) pour condenser les substances
provoquant les odeurs, la vapeur d'eau, etc...., et éventuellement un ou plusieurs
barreaux de protection (6) pour maintenir en place le produit sensible et empêcher
tout contact avec le serpentin de refroidissement et/ou le serpentin chauffant.