EN ISO 15797
Workwear for washing with industrial laundries

The international standard UNI EN ISO 15797 specifies which equipment to use and the test tests to which workwear (including PPE) must be subjected to determine if they are suitable for industrial washing and drying. The tests include parameters such as dimensional stability, colour characteristics, creasing, wrinkling of the seams, pilling and visual aspects in general.

Why industrial washing is important

It is important that all garments, especially certified ones, are properly washed and dried during their maintenance, to ensure that their performance characteristics remain intact over time.

Protective workwear, especially if made with treated fabrics, has decay properties. For this reason, the maximum number of washing cycles to which they can be subjected is specified on the garment labels.

Industrial laundries are equipped with an electronic counting system (transponder hips or electronic labels applied to the garment), which takes into account the different washes of each garment.

Another important service is that of sanitation. Hospitals, hoteliers, restaurateurs, for example, use industrial laundries which guarantee them the hygiene standard required by their category.

The washing process

The EN ISO 15797 standard includes a table to refer to for washing and drying instructions:

Process Number	Classification	Type of fabric
1 – 2	White or with colourful decorations workwear. Treatment with peracetic acid	Cotton and Polyester/Cotton
3 – 4	White workwear. Treatment with peracetic acid	Cotton and Polyester/Cotton
5 – 6	White or with colourful decorations workwear. Treatment with sodium hypochlorite​	Cotton and Polyester/Cotton
7 – 8	Colorful workwear	Cotton and Polyester/Cotton

This table divides garments into four processes based on the color, the type of treatment they can undergo and the fabric:

• The first classification (1 and 2), regulates the treatment of white workwear or garments with delicate coloured decorations. Washing takes place at a temperature of 75°C and peracetic acid is used as a bleaching agent.
• The second classification (3 and 4) defines a process suitable only for white workwear washed at temperatures of about 85°C/75°C according to the load, which are bleached with sodium hypochlorite. During the rinsing phase, a reducing product (sodium metabisulfite or sodium sulphite for example) is added to completely eliminate chlorine residues.
• The third classification (5 and 6) includes the washing of only white workwear or garments with sensitive-coloured decorations that are bleached with hydrogen peroxide at a temperature of 85°C.
• The last classification (7 and 8) requires washing of only coloured workwear treated without a bleaching agent at a temperature of about 85°/75°C depending on the load..

In all four classifications, the moisture content of garments after washing varies between 50% and 55% for full load washing and between 35% and 40% for light load washing.

Detergents and bleaching agents

The EN ISO 15797 standard sets particular importance on the use of detergents by proposing mainly two types: one containing optical brighteners, which cannot be used assessing colour characteristics, and one without optical brighteners.

The specific features of detergents are important, which is why the standard requires them to be traceable as regards manufacturer, batch number, date and production.

Regarding the bleaching agents provided, they are all oxidizing substances whose chemical composition is specified by the standard itself: hydrogen peroxide, with not particularly aggressive oxidizing power, sodium hypochlorite, which has a particularly aggressive action on colours and could cause even significant shrinkage, and peracetic acid.

In all three cases, the bleaching effect derives from the release, during use, of active oxygen (in the case of peracetic acid and hydrogen peroxide) and of active chlorine (in the case of sodium hypochlorite).

The drying process

There are two procedures for drying clothes:

Tumble dry, tumble dryer (A) at temperatures not exceeding 90°C.

The garment is considered dry when it reaches a relative humidity of between 0% and approximately 3%.

Tunnel drying (B) with an air temperature of 155°C.

The garment is considered dry when it reaches a temperature between 135°C and 140°C.

EXAMPLES

In this case, it is a white or decorated garment made of Cotton:

In this case, it is a white or decorated garment made of Cotton. It should be treated with peracetic acid and dried in a drum or in a tunnel.

In this case, instead, the garment, in Cotton or Cotton/Polyester, white or with coloured decorations, can be treated with peracetic acid or hydrogen peroxide. Tunnel drying is only possible.