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Protection against cold conditions
Clothing is the most important personal protection against cold, windy and moist environment. The cold protective clothing must be selected not only according to ambient conditions but work load have to take into account. This project reported that especially wind was experienced a problem while working outdoors in the arctic open-pit mines, and clothing selection was related to exposure time, work load, environmental conditions and personal sensitivity to cold.
Clean clothes are warmer than dirty ones; dirt blocks the structure of the textile and prevents moisture from transferring from the skin. Frequent use and washing of the clothing lowers thermal insulation of the clothing about 20%.
Wear layers in the cold
Layered clothing provides higher thermal insulation due to insulating air layers between the garment layers than single thick fabrics. Still air have about ten times higher thermal insulation than textile materials an average. The layered clothing enables adjustment of clothing depending on the work and ambient temperature.
The individual layers and their functions of the layered winter clothing:
The inner layer keeps the skin dry and warm. It transfers moisture from the skin to the outer layers. Suitable materials are wool (WO), silk (SE), polyester (PES), polypropylene (PP), and two-layer materials. The skin feels dry when you use materials that transfer moisture such as polyester or polypropylene, and when the outer layer is wool.
The middle layer adjusts the thermal insulation of clothing depending on the weather or work load. Suitable materials are wool, fleece and synthetic fur. 1-3 mid layers of clothing are sufficient.
The outermost layer protects against external exposures, e.g. cold, wind, moisture, and dust. The garments should be loose-fitting so that the layers underneath are not pressed and there is enough air inside the clothing. The outermost layer should be one size larger than one’s normal size. Suitable materials are fabrics that protect against moisture and wind. Visibility is enhanced by using reflective colours and reflectors (EN ISO 20471:2013).
The open-pit mines do not have natural shelter, e.g. trees, against wind. Cold wind increases the heat loss of clothing, as it conveys heat away from the clothing. Therefore, cold protective clothing should include tightening straps or similar in jacket hem, waist, neckline, sleeve and leg ends, to prevent effect of wind.
During work in the open-pit mine in winter, 75% of workers get their clothing wet due to sweating or external moisture, such as snow, water, or sleet. Moisture in the clothing decrease thermal insulation and increase the evaporative heat loss from the body. If clothing get wet during work, it should be able to dry between work shifts.
Protection of extremities
Among workers in open-pit mines fingers and toes were experienced the most often the coldest areas of the body. Gloves are often removed during tasks requiring manual dexterity, and about 60% of workers in the open-pit mine experienced that bare hand contact with cold objects was a problem in the cold.
Hand protection consists of different layers. Wear thin gloves underneath and thicker ones on top, so that you never need to have bare hands. Mittens give more protection than gloves. Remember to take an extra pair of gloves with you so that you can change them if they get wet.
Feet protection is most effective when you wear two pairs of socks. Wear socks made of synthetic materials underneath, and woolen socks that have good thermal insulation on top. Cotton is not a suitable material in cold weather because of its cooling effect when it is wet.
Winter shoes should be one size larger than summer shoes. They should have a thick outsole to protect against the heat transfer from the feet to the ground and a high leg to protect the ankles. Insulation can be increased by using insoles/insocks made of felt or other insulating material.
Head protection is important in cold weather, as most heat is lost from the uncovered head. The head should be protected against cold, wind and moisture. Make sure to protect the ears and face because they get cold most easily. You can adjust your clothing by using e.g. a scarf, hood, face guard.
Results from the project
Results from the questionnaire study shows that clothing was selected based on exposure time, work load, environmental conditions and sensitivity to cold. On the other hand, field measurements revealed that clothing was not adjusted according to ambient temperature. Moreover, there was a clear imbalance in the clothing thermal insulation between torso and legs. Wind lowered thermal insulation by 18–30%. Use and washing of the clothing decreased dry and wet thermal insulation by about 20%, but improved wind protection.
- Jussila et al. (2014) Requirements for cold protective clothing at arctic open-pit mines (abstract)
- Jussila et al. (2014) Evaluating cold protective clothing of arctic open-pit miners – Thermal manikin tests (abstract)
- Mänttäri et al. (2014) Summary of the results of questionnaire obtained from the MineHealth project in Kevitsa mine spring 2013
- Rissanen et al. (2014) Dry heat loss in different body parts during work in arctic open-pit mines (4BOHW abstract and poster)
Standards related to protection against cold
There are a lot of standards which determines the requirements, adequacy and evaluation methods for cold protective clothing and gloves as well as e.g. ambient thermal conditions and human thermal strain. See e.g. the abstracts of Jussila (page 23) and Rintamäki and Rissanen (page 47) in: http://minehealth.eu/wp-content/uploads/2012/10/Abstract-book-of-the-3rd-Barents-Occupational-Health-Workshop.pdf
Cold protective clothing is evaluated according to standard EN 342 and is then marked with the pictogram of snowflake. The most important properties of the cold protective clothing are thermal insulation and air permeability. At heavy work or in moist ambient water vapour permeability and resistance to water penetration are important properties. Cold protective gloves are evaluated according to European standard EN 511.
- Ilmarinen et al. (2011) Hypotermia – Kylmän haitat työssä ja vapaa-aikana (Työterveyslaitos, in Finnish)
- Risikko and Marttila-Vesalainen (2006) Vaatteet ja Haasteet (in Finnish)
- Hassi et al. (2002) Opas kylmätyöhön. Työterveyslaitoksen julkaisuja. (in Finnish)
- MineHealth project: http://minehealth.eu/publications/