Spontaneous Combustion: How Oily Towels Become a Fire Risk

Can oily towels really combust on their own? Under specific conditions, the answer is, amazingly, yes. Although uncommon, this phenomenon can occur in gyms, clinics and leisure facilities where oil-contaminated towels are handled routinely.

It sounds unbelievable at first. A towel used to wipe massage oils from a physiotherapy bench is left scrunched up, and hours later, it begins to smoulder or even catch fire. Yet this scenario is real, and it’s a recognised fire safety phenomenon known as spontaneous ignition or self-heating. While rare, it’s well-documented in fire safety guidance and entirely preventable once you know the science behind it.

How Does It Happen?

The key ingredients for spontaneous combustion of oily towels are surprisingly simple:

OIL + OXYGEN + HEAT TRAPPED IN FABRIC

Many medical and therapy oils, particularly plant-based oils, contain unsaturated fatty acids, which can react slowly with oxygen in the air. This reaction, called oxidation, releases heat. Normally, that heat is harmless and dissipates into the surrounding air.

However, when oil is absorbed into a porous fabric like a towel, the oil is spread across thousands of tiny fibres. This massively increases its surface area and contact with oxygen, accelerating the oxidation process.

If that towel is then scrunched up or piled, the fabric acts like insulation. Heat becomes trapped inside the bundle. As the temperature rises, the oxidation reaction speeds up, producing even more heat in what is known as a runaway effect. In the right conditions, this can lead to smouldering and, in extreme cases, ignition.

This is why fire authorities frequently warn about oily rags in workshops, and why the same principle can apply to towels and linens in clinical settings, where certain everyday practices can unintentionally create the right conditions:

• Repeated wiping of benches and plinths, increasing oil saturation in towels
• Used towels placed straight into laundry baskets or bags
• Towels left overnight in warm rooms or near radiators
• End-of-day cleaning when attention is understandably lower

Importantly, this risk isn’t limited to one specific oil. While “drying oils” like linseed are the classic example, the underlying mechanism is heat-producing oxidation, which can occur to varying degrees in many organic oils depending on quantity, temperature, ventilation, and how the fabric is stored.

Even when towels have been washed, the risk is still there. Laundered towels can spontaneously combust after being in the dryer, even hours later. This occurs when towels contaminated with essential oils or beauty products are washed but not fully cleaned of oil residue.

The biggest risk comes from the scrunching and piling of oil-contaminated towels. A flat or well-ventilated towel can safely lose heat as it’s generated, while a bunched-up towel cannot. This is why the most consistent advice across fire safety guidance is simple: never leave oil-contaminated cloths crumpled or piled.

Physiotherapy benches, leisure club furniture and medical furniture are regularly cleaned of oils with towels, which can become a fire risk if not properly stored afterwards.

Medical & Clinical Oils That Can Pose Risks

In medical, clinical, and leisure settings, there are several oils and oil-based products that can present a self-heating / spontaneous-combustion risk when they soak into fabrics and are left bunched up.

1. Emollient Oils (Skin & Wound Care)

Used widely in dermatology, elderly care, long-term inpatient care and pressure sore prevention, many emollients contain plant oils or blended formulations that can oxidise when absorbed into towels, bedding, or dressings. This is one of the most documented clinical contexts for fabric-related fire risk, and fire services have repeatedly warned about oil-soaked bedding and clothing in care environments.

Examples:

• Emollient bath oils
• Paraffin-based skin oils blended with plant oils
• Barrier oils used during dressing changes

2. Physiotherapy & Rehabilitation Oils

Beyond massage, these oils are also used for joint mobilisation, manual therapy and sports rehab within clinical settings. These are unsaturated plant oils, which oxidise more readily than mineral or wax-based alternatives, especially when repeatedly absorbed into towels used throughout the day.

Examples:

• Sweet almond oil
• Grapeseed oil
• Sunflower oil
• Blended “professional glide” oils

3. Topical Anti-Inflammatory or Therapeutic Oils

Commonly used in pain clinics, sports medicine and rehabilitation units, these oils are often applied in small amounts but repeatedly, leading to gradual oil loading of cloths, wraps, or reusable supports.

Examples:

• Oil-based analgesic rubs
• Herbal or botanical therapeutic oils
• Compounded topical preparations

4. Medical Lubricants with Organic Oil Content

While many modern medical lubricants are water- or silicone-based, legacy or specialist products may still contain organic oils capable of oxidation. Medical lubricants are commonly used for equipment preparation, skin protection during procedures and certain diagnostic or therapeutic devices.

Examples:

• Oil-based lubricants (non-silicone)
• Hybrid products containing both mineral and plant oils

5. Essential Oil Blends Used Therapeutically

Essential oils alone are not the main combustion risk due to small quantities, but they are almost always diluted into carrier oils. Towels used during aromatherapy may still become oil-contaminated, where the carrier oil, not the essential oil, is the relevant risk factor.

Common uses of essential oils:

• Mental health units
• Palliative care
• Complementary therapy within healthcare

Oils That Are Less Likely to Contribute (But Not Zero-Risk)

Some oils used within clinical settings present a lower risk of oxidation, but even these should not be considered fire-proof once absorbed into fabric. The risk is lower, not eliminated, especially if towels are heavily loaded and tightly piled.

• Mineral (liquid paraffin) oil, which is chemically inert
• Jojoba oil, which is a wax ester and highly oxidation-resistant
• Silicone-based medical lubricants, which are exceptionally resistant to oxidation

How Clinics Can Prevent This

The good news is that prevention is straightforward and inexpensive. Best-practice controls include:

• Do not scrunch or pile oily towels. Spread them out fully or hang them so heat can dissipate.
• Wet storage until laundering. Place oil-contaminated towels in a metal container with water if they can’t be washed immediately. Water prevents oxygen access and absorbs heat.
• Separate oil-contaminated linen. Use a clearly labelled container or bag so these towels aren’t mixed unknowingly with dry laundry.
• Keep away from heat sources. Avoid leaving used towels near radiators, dryers, or in warm enclosed cupboards.
• Train staff and standardise the process. A short, written SOP for “oil-contaminated towel handling” dramatically reduces risk.

For laundered towels, key safety measures include:

• Allow Cooling: Never stack or pack away warm, freshly dried towels. Let them cool completely.
• Proper Washing: Wash towels contaminated with oils at high temperatures (ideally above 90°C) to break down and remove residues.
• Use the Dryer Cycle: Always let the dryer finish its full, cold-air cycle; do not stop the machine early.
• Don’t Pile Immediately: Avoid piling hot, laundered items into baskets, which traps heat.

While rare, self-heating can give warning signs. A towel that feels unusually warm, a sharp or acrid “oil” smell, and visible smoke or smouldering are all indicators that the combustion process has begun. If this occurs, isolate the towel on a non-combustible surface, wet it thoroughly if safe to do so, and follow your site’s fire safety procedures.

At Gym Wizard and our sister companies, MediWizard and Yorx, we talk a lot about hygiene, durability, and occupant safety. But safety also includes understanding less obvious risks in everyday routines. A safety culture goes beyond cleanliness. By making small changes to how oil-contaminated towels are handled, clinics can eliminate a hidden fire hazard, protecting staff, guests, and facilities alike.