If you’re on massage forums for more than a few months, you’ll occasionally see something pretty scary: A picture of burnt sheets, and a post describing the smell of smoke followed by a quick evacuation. There are even news articles every year or two of building fires caused by massage linens. This issue is underdiscussed (other than by ABMP, which stays on top of it), despite it being a concern specific to our industry, and despite it being something we can mitigate! So, let’s discuss.

To start, what the heck is happening? What we’re talking about here is spontaneous combustion. That’s where there’s no spark or other ignition source, but material still manages to accumulate enough heat to set it aflame. This happens to massage linens because oil oxidation is an exothermic reaction. As oxygen shacks up with oil molecules, a small amount of heat is released. This leaves you with stubborn oil stains (the oil polymerizes, making it less soluble), and a bad smell — oxidized oil is rancid oil.

Still with me? Oily sheets + air = heat. Then, hot oily sheets + air = lots of heat! Oxidation happens more rapidly as a material heats up, making this a positive feedback loop, with the process accelerating over time. A great discussion of this in other industries can be found here.

The thing is, when dealing with massage linens, this usually peters out, resulting in nothing but sheets with a musty smell and an oily sheen. The heat from the exothermic reaction is able to diffuse away before the temperature of ignition is reached, or there’s not enough unoxidized oil to keep feeding the reaction. This is true the vast majority of the time, and it’s one reason I don’t want you to be too paranoid about your sheets combusting: Most of us keep sheets in service for months and months without issue.

But! Sometimes things go wrong, and it’s not exactly predictable. Some massage therapists use visibly oily sheets for years longer than they should, convincing themselves that their clients don’t notice, but: No combustion. Some massage therapists go about their washing and drying routine for years without a problem, and then one day, their smoke alarm goes off. What gives?

What Makes Good Oil Go Bad?

If you’ve read about these incidents, you’ll notice some common themes: Linens left in tightly packed bundles; hot cars; and unattended dryers. We’ll talk about why each of these is dangerous, thermodynamically speaking:

• Why are tightly packed linens dangerous? Oily linens, before or after laundering, usually go about oxidation at a fairly sedate pace. That’s fine! But: If you were to cram those same sheets as tightly as possible into a bag (at least one incident involved a tightly packed backpack), that might make it difficult for heat to dissipate from the center of the wad. The lesson here: When it comes to oily cloth, loosely packed is better than tightly packed.
• What if you were to leave those linens in a hot car? No matter how tightly they’re packed, they’re going to undergo oxidation more rapidly, and they’ll be worse at shedding the heat from that reaction. This heat accumulation is called “thermal runaway,” and it can get out of hand quickly. The lesson: If it’s a hot day, haul your linens with you instead of leaving them unattended in your car.
• And finally, we’ve got the unattended dryer, which seems to be involved in most of the combustion incidents I’ve seen massage therapists describe. Things go as normal: You wash a set or two of sheets, dry a set or two, and leave the last set in the dryer to fold the following morning. Usually fine! But this is a habit we need to break.

Here’s what happens: Your ostensibly clean sheets still have some oil left over, and that oil has spent the last 45 minutes being blasted with hot air. This is a VERY good environment for rapid oxidation. The cooldown interval at the end might slow this down, but you’re still left with oily cloth undergoing oxidation in a well-insulated chamber. That wad of fabric is going to have a very hard time shedding heat, and so thermal runaway is more likely. The lesson here: Always remove sheets and towels from the dryer when you hear the buzzer, and then either leave them in a loose distribution on a flat surface (not crammed in a basket), or go ahead and fold them. Doing that will remove most of the remaining heat, and the folded shape is less adept at acting as an insulator (though stacks of sheets in a closed drawer can be a problem).

Curing Your Oil Concerns

Some other ways to reduce the odds of combustion:

• Wash your linens frequently rather than keeping many sets that you wash at the end of the work week. The longer you allow oily cloth to sit, the more that oil will polymerize, and the less will wash out. The more partially oxidized oil that accumulates on your sheets, the more reactant there will be. Throw out sheets that smell musty, or that have visible staining.
• Try oil that oxidizes more slowly. Jojoba and coconut oil take a long time to oxidize — less musty smell, less chance of thermal runaway. Almond oil can oxidize fairly quickly, and hemp oil just loves going rancid (see the pdf link on this page). If you use almond oil or something else that oxidizes quickly: Wash soon after use, use a laundry detergent that degreases well, and consider changing out for brand new sheets on a set schedule.
• You could also try using an emulsified massage medium, like lotion, cream, or gel. These products mix oil and water using an emulsifier, so they’re more likely to wash out, though you’ll still see accumulation over time.

ALL THAT SAID: No matter how careful you are, oil still builds up, and oxidation is always happening. The tips above can help, but we work with oily cloth, and spontaneous combustion is a hazard we face. The upshot: Use your best practices, AND keep working (and tested!) smoke detectors and a fire extinguisher nearby.

Be safe, be aware, and thanks for joining me on Massage Linen Spontaneous Combustion Awareness Day.