Fire Risk in Stenter Machines and Dryers

How does a stenter fire start?

A stenter (tentering and heat-setting) machine holds the fabric by its edges to adjust its width, dries it and fixes finishing chemicals. To do this, it passes the fabric through a long hot-air chamber. Some of the spinning oils, softeners and other finishing agents on the fabric evaporate at this temperature and are carried out with the exhaust air. On cooler surfaces such as the exhaust duct, fan, filter or heat recovery unit, this vapour condenses and leaves a sticky, oily residue. Fibre and lint shed by the fabric cling to this residue, forming a layer that thickens over time and ignites easily.

A stenter fire usually starts when this layer is ignited by a hot surface, a burner flame or a spark, and it spreads rapidly along the duct. Fires involving oily residue can reignite even after being extinguished. A similar mechanism is seen in other textile dryer fire scenarios involving hot air.

Textiles are one of Bursa’s leading sectors; TOSAB Bursa Textile Dyehouses Specialised OIZ in the Badırga area of Nilüfer is an organised industrial zone dedicated to dyehouses. In the 2025 list of hazard classes, textile bleaching and dyeing (NACE 13.30.01) is in the hazardous class. For other risks in dyeing and finishing businesses, see our article on textile dyeing and finishing.

Oil, fibre and heat: where build-up forms

A cleaning plan starts with knowing where build-up forms:

The rate of build-up varies with the type of fabric processed, the chemicals used, the operating temperature and the exhaust arrangement. So instead of a fixed frequency such as “once a month”, a frequency that starts from the manufacturer’s instructions and is adjusted according to the residue thickness measured on site is more reliable.

Stenter cleaning: planning, lockout and records

Stenter cleaning is a job that both prevents fire and carries risks of its own. Safe cleaning includes the following steps:

1. Cooling down: The machine is stopped, the burner or thermal oil circuit is shut off, and you wait until the chamber has cooled to a temperature at which cleaning can be done.
2. Energy isolation: The chain drive, fans, burner and fuel line are locked and tagged. If a fan is started while someone is cleaning, serious injury can result. For details, see our LOTO article.
3. Confined space assessment: If someone will enter the duct or unit, it is assessed as a confined space; an entry permit, gas measurement and a standby person are needed.
4. Suitable tools and materials: Non-sparking scrapers are used; the safety data sheet of the cleaning chemical is checked.
5. Separating hot work: If welding or grinding is needed during cleaning, a separate hot work permit is issued; no hot work is done near oily residue.
6. Records: The cleaning date, area cleaned, observations on residue thickness and the person who did it are written on the form.

Stenter exhaust oil build-up and the exhaust line

Stenter exhaust oil build-up is the risk most easily overlooked, because the duct and stack are usually at ceiling level or on the roof and their insides cannot be seen. The following arrangements on the duct line make cleaning and inspection easier:

• Cleaning hatches: Hatches along the duct, especially at bends and changes of direction, through which it can be inspected and cleaned
• Condensate collection: Falls and drain points where oil can be collected and drained
• Temperature monitoring: An alarm on a sudden rise in duct or exhaust temperature
• Separate exhaust lines: If more than one stenter is connected to the same stack, assessing the likelihood of a fire in one machine reaching the others via the ducts

Heat recovery and emission control units are beneficial for energy and the environment, but because they are where oil collects, they are also critical points for fire. These units should be cleaned according to the manufacturer’s instructions and with records kept.

Stenter extinguishing system and detection

When a fire starts inside the chamber or duct, tackling it with a portable extinguisher is usually inadequate and puts the worker at risk. This is why a machine-specific stenter extinguishing system is important. In practice, water mist, sprinkler, steam or gas extinguishing systems installed inside the chamber and duct according to the machine manufacturer’s design are used. Whichever system is chosen, the following features should be required:

• Detection: Temperature or flame detectors in the chamber and duct
• Automatic shutdown: The burner or heating circuit cut off at the moment of detection, and fans stopped in a way suited to the fire scenario
• Manual release: A button with which the operator can activate the system from a safe point

Fire extinguishing installations, sprinklers and detection systems undergo periodic inspection at least once a year under Annex III of the Regulation on Health and Safety Requirements for the Use of Work Equipment; fire measures for the building as a whole are assessed within the framework of the Regulation on the Fire Protection of Buildings. For the type of portable extinguishers to keep around the stenter, see our article on types of fire extinguishers.

What the stenter operator does in a fire

In stenter fires, the right steps in the first minute determine whether the fire stays in the chamber or spreads along the duct. The general sequence the operator must learn is as follows; the details should be written according to the machine’s emergency instruction:

1. Emergency stop and cutting off the heating
2. Raising the alarm and moving workers away from the section
3. Triggering the fixed extinguishing system manually if it has not activated automatically
4. If the fire is in its initial stage and there is a safe escape route, tackling it with a portable extinguisher by trained persons
5. If the fire is growing, abandoning the response, evacuating and calling 112
6. After extinguishing, monitoring the chamber and duct for reignition

So that this sequence does not stay on paper, a scenario specific to the stenter section should be included in one of the drills held at least once a year.

Common mistakes in the stenter section

The weaknesses that pave the way for stenter fires are similar in most businesses. Check your own section against this list:

• Cleaning sacrificed for production: In busy order periods, planned cleaning is postponed, yet build-up speeds up precisely in these periods when the machine runs longest.
• Cleaning only what is visible: The inside of the chamber and the screens are cleaned, while the duct and fan at ceiling level are not opened for years.
• Unrecorded cleaning: If when, where and by whom cleaning was done is not written down, no one knows when the next cleaning is needed either.
• Disabled detection: Disabling a sensor that gives frequent false alarms can leave the whole system ineffective. The cause of the false alarm should be eliminated, not the sensor disabled.
• Combustible stock around the machine: Chemical drums, packaging material and fabric rolls are piled up around the stenter. For storing flammable liquids, see our article on the storage of flammable liquids.
• Only one operator knowing: If only one person knows how to trigger the fixed extinguishing system manually, the system effectively does not exist on a shift when that person is absent.

Reflecting this in the risk assessment and fire training

Stenter fire should be addressed machine by machine in the risk assessment: which fabrics and chemicals are processed, where build-up forms, who cleans and how often, and how the extinguishing system works. A fire or near miss events such as a small flare-up require the risk assessment to be renewed without waiting for its validity period to expire. For general measures, see our article on the workplace fire prevention checklist.

We provide theoretical and practical fire training; we plan the fire training programme for stenter operators and the firefighting team with machine-specific scenarios. In our risk assessment service, we link the cleaning plan, lockout steps and inspection of the extinguishing system to the document. For obligations specific to textile businesses, see our textile sector and Nilüfer OSGB pages, and for drill and inspection dates, our OHS calendar tool.

Frequently Asked Questions

How often should a stenter be cleaned?

There is no fixed legal frequency. The manufacturer’s instructions are the starting point, and the frequency is adjusted according to the residue thickness observed on site and the fabrics and chemicals processed. In-chamber screens and filters are cleaned much more often than the duct and stack.

Is a stenter fire put out with water?

Fixed systems inside the machine may use water mist, sprinklers, steam or gas according to the manufacturer’s design. Tackling a fire with water around electrical panels and the burner carries separate risks; choose the type of portable extinguisher according to the fire class, and have only trained persons respond.

Which permits are needed for stack cleaning?

At least lockout and tagout is needed. If someone will enter the duct or unit, a confined space entry permit is also issued, and if welding or grinding will be done, a hot work permit.

How often is the extinguishing system inspected?

Fire extinguishing installations and detection systems undergo periodic inspection at least once a year under Annex III of the Work Equipment Regulation. If the manufacturer specifies a shorter maintenance interval, that interval applies.