Gas masks and asbestos

On the right is a military-green rubber gas mask, with eyepieces facing towards the photographer. Next to it on the left is a darker green filter cartridge. At the bottom is a scale.
A civil defence gas mask from the late 1930s included in the collections of the Helsinki University Museum. The gas mask originally belonged to the University of Helsinki Department of Pharmacology. Photo: Helsinki University Museum.

The collections of the Helsinki University Museum include eight gas masks, of which seven are from the 1930s and intended for the civilian population. The University Museum has received the masks from hospitals and University of Helsinki departments. The collections also include an equine gas mask dating back to the 1930s or 1940s which is of an unknown origin.

In 2015 we made plans to place one of the civilian gas masks on display in the University Museum’s new main exhibition, The Power of Thought. However, we had to scrap these plans at the last minute when we discovered that the filters of old gas masks may contain asbestos.

In spring 2020 we decided to find out whether these suspicions were true. In this blog post, we explain how we investigated the matter and what we eventually found out.

Asbestos in filter cartridges

The connection between the filter cartridges of old gas masks and asbestos has long been known around the world. However, the focus has been on the workers of factories producing gas masks during the Second World War whose health and causes of death were analysed in the 1970s and 1980s in Britain and Canada, for instance. Those exposed to asbestos at work have suffered from, for example, lung cancer, to a far greater degree than other members of the population.

An illustration published in the Hakkapeliitta magazine shows three men wearing boilersuits and gas masks during a drill. The men are standing with their hands on their hips, bending their upper body to the side. The illustration is in black and white.
“Gas mask drills. Breathe calmly!” Breathing through a gas mask was hard, which is why it was recommended that people get gradually used to it through various drills. Photo: Guarding against the danger of gas. Hakkapeliitta, Issue 23, 1931, p. 682.

No research-based information is evidently available on the asbestos exposure of contemporary gas mask wearers or current gas mask owners and wearers. Possible risks were not properly addressed until the 2000s.

In 2014 the UK Health and Safety Executive (HSE) investigated 34 old British and German gas masks. The results showed that the filters of 29 gas masks contained asbestos, and six filters included blue asbestos, considered the most hazardous for health. The HSE decided that old untested gas masks should not be handled or worn as teaching aids in schools because visually distinguishing between hazardous and safe filters is difficult or impossible.

A black-and-white photo of six men in battledress standing side by side outdoors. The men are demonstrating each stage of putting on a gas mask: the first man is taking a mask from a bag around his neck, the second is holding a mask in his hands, the third is placing a mask on his face, the fourth is putting the hose in place, the fifth is making the final adjustments and the sixth is ready.
Six soldiers demonstrating the use of a gas mask during the First World War. Photo: Wellcome Collection. CC BY 4.0.

In Finland, the issue of asbestos in gas masks first arose in public in 2017 when the Varusteleka Oy company, among others, had to stop selling filter cartridges for the Soviet GP-5 and PDF-2 gas masks and ask customers to return any cartridges they had bought. The recall was initiated by the Finnish Safety and Chemicals Agency, which had had 12 filters from the 1980s tested by the Finnish Institute of Occupational Health. Asbestos had been found in the particulate filter layers of all filters.

The presence of asbestos is characteristic of the filter layers of old gas masks made not only in Britain, Germany and the Soviet Union, but also in other countries. The phenomenon affects museums, schools, collectors and hobbyists alike. Asbestos can also have been used in filters manufactured in Finland. For example, Väestönsuojeluopas, a guide published by the Finnish civil defence organisation Suomen Väestönsuojelujärjestö in 1962, features a structural drawing of a gas mask filter. The dust filter is said to be made of cellulose and asbestos fibre.

Old gas masks are common in museum collections, but they are particularly popular among collectors. Many of the collectors acquire gas masks for their own use, to wear.

Three little girls on a street wearing gas masks. Two of the girls have a bicycle. Many wooden chairs can be seen in the background. The image is in black and white.
Gas masks have also been produced for children. This photograph was taken for the British Daily Herald newspaper in ca 1940. Photo: Daily Herald Collection at the National Science and Media Museum, Bradford. CC BY 4.0.

Authorities throughout the world have warned that, as a gas mask filter ages, it can become brittle, in which case asbestos fibres will be released into the air for the wearer to breathe in, and possibly onto the surfaces of the gas mask and the bag it is kept in. The asbestos issue has also received increasing attention from international hobbyists. It is generally recommended in online forums and chatrooms for hobbyists that old filters be replaced with new, safer ones. However, a significant number of the owners and wearers of historical gas masks are unaware of the risks.

Due to the lack of research-based information, it is difficult to say with certainty how easily asbestos fibres are released into the air outside the filter and whether asbestos fibres released from a particulate filter layer can pass through an active charcoal filter and enter the wearer’s respiratory tract. Similarly, we do not know how likely this is and how significant a health risk asbestos poses to hobbyists, collectors and museum staff.

Development of gas masks

Chemical warfare was invented before the Common Era, but the more extensive use of chemical weapons dates back to the First World War. The poison gases used included various chemical substances, such as the corrosive mustard gas, which caused severe skin and lung damage. Serious cases of mustard gas poisoning led to the victim’s death in just a few days or weeks.

The new weapons required new types of protection. The predecessor of the modern gas mask had been patented in the United States as early as the mid-1800s, and it was capable of filtering particulates from the air. After 5,000 French soldiers died in April 1915 of the chlorine gas released by the Germans during the Battle of Ypres in Belgium, several countries made frantic efforts to develop gas masks and filters. For example, a gas mask based on an activated charcoal filter was developed in Russia that same year.

An early gas mask, with the mask itself made of brown leather. The gas mask includes circular eyepieces with metal rings as well as a metal filter.
German-manufactured gas mask, ca 1915–1918. Photo: Board of Trustees of the Science Museum. CC BY 4.0.

The First World War eventually came to an end, but concerns about chemical warfare have not abated. Despite the use of gas weapons having been prohibited by the 1899 Hague Declaration Concerning Asphyxiating Gases and the 1907 Hague Convention on Land Warfare, both parties to the war had used poison gases extensively, killing a total of 90,000 people. It appeared evident that the use of these weapons would continue in future wars and conflicts.

Finland began to prepare for the use of poison gases in the 1920s. Suomen Kaasupuolustusyhdistys, an association for defence against gas weapons, was established in 1927, and as of 1930, this association functioned as an organisation known as Suomen Kaasupuolustusjärjestö. The duties of the organisation included public education and training, and it also held gas defence demonstrations, published the popular Kaasutorjunta magazine and sold Finnish civilian gas masks.

Gas masks equipped with various filters and features were manufactured for various uses. Servicemen required more efficient protection than civilians. Finnish newspapers published instructions for making gas masks at home, and in the most acute emergencies, people could also protect themselves against chemicals with, for example, moss, a wet cloth or a tissue filled with soil, sawdust or crushed charcoal.

Gas masks for the civilian population in the Helsinki University Museum’s collections

Two gas masks side by side. The masks are made of rubber covered by a green fabric. Below the masks is a scale. Next to one of the masks is a small cylinder-shaped package with the word Lasisaippua (‘Glass soap’).
Two Finnish civilian gas masks from the early 1930s. The Helsinki University Museum received the masks from the former Helsinki University Library, now the National Library of Finland. Photo: Helsinki University Museum / Anders Manns.

The collections of the Helsinki University Museum include two types of gas masks for the civilian population: Finnish civilian gas masks from the early 1930s and civil defence gas masks from the late 1930s.

The manufacture of Finnish civilian gas masks began in 1930. Thousands of such masks were sold to members of the public, and the Belgian government also ordered a large batch. The user manual for the masks from 1931 explains that the filter contains “50 parts by weight of activated mask charcoal and 50 parts by weight of special soda lime” and that the filter does not protect from dusty forms of poison gases. However, separate ‘dust filters’ were available for the civilian gas mask. Because asbestos has been found to be associated with particulate filters, a filter used only for gas protection should not contain asbestos. However, asbestos may be present in a ‘dust filter’, but no such item is included in the University Museum’s collections.

An oval half-length newspaper portrait of a man wearing a Finnish civilian gas mask, a white shirt with a collar, a dark jacket and a bow tie. A strap over the man’s shoulder is presumably that of the gas mask bag. The image is in black and white.
Civilian gas masks were introduced on the market in 1930 for the reasonable price of 150 markka, or just over €50 in today’s currency. The price for members of Suomen Kaasupuolustusyhdistys was just 60 markka, or €20. Photo: Civilian gas defence. Kansan Kuvalehti, Issue 21, 1930, p. 13.

In late 1938, the Suomen Kaasupuolustusjärjestö organisation developed a new civil defence mask for civilian use, with small adjustments made to the mask early next year. The civil defence gas masks that entered the market in early 1939 included the filter for the civil defence force gas mask M/38, but subsequent masks included the filter for civil defence gas mask M/39 with separate gas and dust filter layers and a filter with lower profile. The existence of the dust filter layer indicates the possible presence of asbestos. Gas mask collector Liam Robinson also believes that the filter cartridge of the Finnish civil defence mask M/39 contains asbestos.

Green gas mask in a cardboard box. Finnish- and Swedish-language instructions for the use and care of the mask are printed inside the lid of the cardboard box.
The civil defence mask M/39 belonged to Salli Eskola, assistant at the University of Helsinki Department of Chemistry, who became Finland’s first female chemistry professor in 1947. The mask includes a low-profile filter equipped with gas and dust filter layers. Photo: Helsinki University Museum / Sanna-Mari Niemi.

Results of the asbestos analyses of the Finnish Institute of Occupational Health

Because the issue of asbestos in gas masks had troubled the staff of the Helsinki University Museum for years, we decided to contact the Finnish Institute of Occupational Health in spring 2020 to enquire about the possible analysis of these objects. Specialist Annika Lindström became intrigued because she had investigated the Varusteleka filters in 2017, and the question of asbestos fibres passing through the filter had lingered in her mind.

We initially chose four gas masks for analysis: two Finnish civilian gas masks from the early 1930s and two Finnish-made civil defence gas masks from ca 1939. Our hypothesis was that the former would not contain asbestos, while the latter would. Later, we also decided to send the equine gas mask for analysis.

The selected gas masks were delivered to the Finnish Institute of Occupational Health. The purpose was to find out whether the filter cartridges contain any asbestos, and if they do, whether it can be released and end up on gas mask surfaces and cases. Annika Lindström was also interested in studying whether there is any asbestos in the air breathed in by the mask wearer.

The partially opened filter cartridge of a civil defence gas mask. Under the mesh metal plate, denser metal netting can be seen, beneath which is a layer of white cotton-type filter material.
The filter cartridge of civil defence gas mask M/39 was broken open, and a sample was taken of the cotton-type material inside it. The sample was then analysed with an electron microscope. It was found to contain asbestos. Photo: Finnish Institute of Occupational Health.

As expected, the Finnish civilian gas masks from the early 1930s did not contain asbestos. However, asbestos was found in the filter cartridges of both of the civil defence gas masks of 1939, although they are of different types. It was found, above all, in the cotton-type material on the outer side of the filter. The analyses were performed using material samples.

Electron microscope image showing light-coloured oblong asbestos fibres and fibre bundles.
Chrysotile asbestos fibres in a material sample taken from a civil defence gas mask. The sample was observed with an electron microscope at 10,000-fold magnification. Photo: Finnish Institute of Occupational Health.
A dark-green filter cartridge with a protective lid that is slightly open, revealing an orange-coloured metal mesh plate inside.
The longer filter cartridge of the 1939 civil defence gas mask, possibly model M/38. Cotton-type asbestos-containing material is visible through the openings of the metal mesh plate. Photo: Finnish Institute of Occupational Health.

Because the filters of both civil defence gas masks were found to contain asbestos, dust samples previously taken from the surface of the objects as well as from their mask cases were analysed next. These analyses confirmed that both filters had released asbestos fibres. In addition, the protective cardboard partly attached to one of the filters had not prevented the spread of fibres outside. An air sample was also collected from one of the filter cartridges to find out whether asbestos fibres can pass through the active charcoal filter into the mask wearer’s lungs. The asbestos found in the air sample demonstrates that this can, indeed, occur.

Electron microscope image of an individual asbestos fibre bundle.
Asbestos fibres and fibre bundles were found on the surface of both civil defence gas masks and in the dust samples of the case. The samples were observed with an electron microscope at 10000-fold magnification. Photo: Finnish Institute of Occupational Health.

Due to the interesting results obtained from the analyses of human gas masks, the decision was made to investigate the equine gas mask included in the University Museum’s collections. Its filter cartridge differs structurally from that of the civil defence gas masks in that it is more tightly sealed, but the plate at the bottom has an air intake opening with a rubber cap. A grey felt-like fabric can be seen through the rubber cap under the metal netting.

A dust sample taken with a cotton bud through an air intake opening contained a great deal of asbestos fibres, unlike a sample taken from the mask case. It is possible that a more tightly sealed filter does not release asbestos in the environment as easily as models with mesh filter plates, but meaningful conclusions cannot be drawn based on a single filter.

Equine gas mask, including a padded face piece designed to fit over the muzzle as well as a large filter cartridge painted green. The face piece and the filter are connected with a cloth-covered hose.
Equine gas mask included in the University Museum’s veterinary collection and dating back to the 1930s or 1940s. Asbestos has been used as material in the filter layer of the filter cartridge. Photo: Helsinki University Museum / Susanna Paasonen.

Concluding remarks

Although the number of gas masks studied for this blog post is very small, it seems evident that the filter cartridges of old Finnish-made gas masks often contain asbestos.

Gas mask collectors participating in online chatroom conversations have stated that wearing an old gas mask poses a health risk, but claimed that other handling of old gas masks is safe. The analyses conducted by the Finnish Institute of Occupational Health indicate that this view is too optimistic because asbestos fibres can be released from cartridges both when breathing through the filter and during storage and handling. However, it is not very likely that the handling of a gas mask would lead to the release of asbestos fibres in such abundance that the Finnish limit value for asbestos, 0.01 fibres per cubic centimetre in the breathing air, would be exceeded. In contrast, it is possible that asbestos fibres land on room surfaces, which requires action under the decree on health-related conditions of housing. When breathing through a gas mask, the limit value is clearly exceeded.

Because filter cartridges have not been extensively studied, it is difficult to say whether asbestos is only released from certain filter models or whether all asbestos-containing filters are hazardous to health. As long as no detailed information is available, the handling and, above all, wearing of all old gas masks should be avoided. The masks should be stored in a tightly sealed and undamaged plastic bag, for example, in a re-sealable freezer bag.

If a gas mask is to be put on display in a museum exhibition, it must be ensured that the visitors and staff are not exposed to asbestos. At the British Royal Armouries Museum, for example, an asbestos specialist has been commissioned to apply acrylic sealer over the openings of a filter cartridge, thus preventing the release of fibres outside the cartridge.

Henna Sinisalo, curator

Translation: University of Helsinki Language Services.

The author would like to thank Annika Lindström and Heli Lallukka of the Finnish Institute of Occupational Health for the performance and interpretation of analyses as well as productive cooperation.


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