EN ISO 15797
Workwear for washing with industrial laundries

The international standard UNI EN ISO 15797 outlines the equipment to be used and the required tests for workwear (including PPE) to determine their suitability for industrial washing and drying. These tests encompass parameters such as dimensional stability, colour characteristics, creasing, seam wrinkling, pilling, and overall visual aspects.

Why industrial washing is important

It is imperative to properly wash and dry all garments, especially certified ones, during maintenance to ensure that their performance characteristics remain intact over time.

Protective workwear, particularly if constructed from treated fabrics, possesses decay properties. Consequently, the maximum number of washing cycles allowable is indicated on the garment labels

Industrial laundries employ an electronic counting system (transponder chips or electronic labels applied to the garment) to monitor each garment’s individual wash cycles. 

Another significant service offered by industrial laundries is sanitation. Hospitals, hotels, and restaurants, for instance, rely on industrial laundries to meet the hygiene standards required for their respective industries

The washing process

The EN ISO 15797 standard includes a table for reference in 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 coloured decorations workwear. Treatment with sodium hypochlorite​	Cotton and Polyester/Cotton
7 – 8	Coloured workwear	Cotton and Polyester/Cotton

This table categorises garments into four processes based on colour, permissible treatments, and fabric type:

• The first classification (1 and 2) governs the treatment of white workwear or garments with delicate-coloured decorations. Washing is carried out at a temperature of 75°C using peracetic acid as a bleaching agent.

   

• The second classification (3 and 4) defines a process suitable only for white workwear, washed at temperatures around 85°C or 75°C depending on the load, and bleached with sodium hypochlorite. A reducing product (e.g., sodium metabisulfite or sodium sulphite) is added during rinsing to eliminate chlorine residues.
• The third classification (5 and 6) includes the washing of white workwear or garments with sensitive-coloured decorations, bleached with hydrogen peroxide at a temperature of 85°C.

   

• The final classification (7 and 8) requires washing of  coloured workwear without a bleaching agent at a temperature of approximately 85°C or 75°C depending on the load.

In all four classifications, the moisture content of garments after washing ranges from 50% to 55% for full-load washing and from 35% to 40% for light-load washing.

Detergents and bleaching agents

The EN ISO 15797 standard places significant emphasis on detergents and offers mainly two types: one containing optical brighteners, which should not be used when assessing colour characteristics, and one without optical brighteners.

The specific attributes of detergents are critical, necessitating traceability regarding the manufacturer, batch number, date, and production.

As for the bleaching agents, they are all oxidising substances with chemical compositions specified by the standard itself: hydrogen peroxide, having moderate oxidising power, sodium hypochlorite, which aggressively affects colours and could cause significant shrinkage, and peracetic acid.

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

The drying process

Two drying methods are employed:

Tumble drying, using a tumble dryer (A) at temperatures not exceeding 90°C.

The garment is considered dry when it reaches a relative humidity 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, however, the garment, made of cotton or cotton/polyester, white or with coloured decorations, can be treated with peracetic acid or hydrogen peroxide. Tunnel drying is the only suitable method.