Blue Shop Towels for Masks: Good Filter? Safe? Washable?

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Today I’m investigating if we can use blue shop towels in face masks. Are they a good, breathable filter? Are they washable? And most importantly, are they safe?

Overall, blue shop towels by Toolbox are better at filtering than cotton.

They’re harder to breathe through than an N95 mask, but still manageable.

They’re not washable.

The manufacturer is against people using shop towels in masks. However, they claim no harmful chemicals or fiberglass are in them.

This doesn’t match what Walmart says.

They say Toolbox and Scott’s shop towels contain toxic chemicals known “to cause cancer and/or birth defects or other reproductive harm”.

Then again, the safety data sheet from Toolbox says the opposite…

There are lots of confusing messages about the safety of shop towels. I have contacted the manufacturers for their comments.

blue shop towels for face masks — Photo credit: Sellars.

Contents list:

What are blue shop towels and what are they made of? (Skip to this)
Are blue shop towels good mask filters? (Skip to this)
Are they breathable? (Skip to this)
Are they safe? (Skip to this)
Are they washable? (Skip to this)

What are blue shop towels?

how Toolbox blue shop towels are made in a factory — Blue shop towels being made. Photo credit: Sellars.

Home Depot says they’re absorbent towels “designed for cleaning up grease, liquids, oils and spills in automotive repair shops and garages”.

Blue shop towels from Toolbox are made from:

40% post-consumer paper waste,
fresh tree fibers,
and synthetic latex resin.

paper waste being picked up — Paper waste being recycled for use in shop towels. Photo credit: Sellars.

Here’s a video from Toolbox that shows how shop towels are made:

Are blue shop towels good face mask filters?

Toolbox blue shop towel box — Photo credit: Sellars.

TSI, a particle-testing company, tested 2 layers of blue shop towels from Toolbox. They checked the filtration and breathability of the material twice. They used N95 testing equipment and procedures for better accuracy.

They found that 2 layers of shop towel captured 41.94% to 51.765% of particles.

That’s better than 2 layers of Kona quilting cotton, which only captured 7.02% of particles.

And it’s a lot less than Filti material, which captured 97.851% of particles.

About the test

Here are the particles they tested for:

‘The COVID… virus is smaller than 0.3, at about 0.1 microns, but 0.3 microns is a sort of magic size to test for, according to Kennedy [the President of TSI]. That’s because this size particle is the most difficult to capture, he says. Particles that are bigger, as well as particles that are smaller will be trapped by filters that capture 0.3 microns. So this test of fabrics, “certainly covers the size range for the virus,” Kennedy says.’
J. Bort (2020) on Business Insider [published: 25 April 2020].

Here are some limitations of the study:

“These test results are provided for informational purposes only and do not take into account mask fit or real-world usage, should not be interpreted as recommendation or advice, and are not approved by any regulatory agency.”
TSI & Schemph. Source: https://maskfaq.com/#test-results [accessed: 7 May 2020]

Are shop towels breathable?

In TSI’s study, Toolbox shop towels had a pressure drop of 11.98 to 13.36 mm H20.

Wait, what is mm H20? It’s a way to measure a material’s resistance to airflow.

The higher the number, the harder the material is to breathe through.

For comparison, an N95 is normally 9 mm H20, so the shop towels are harder to breathe through.

It’s still below 15 mm H20, however, which the researchers considered the maximum a material should be.

After 15 mm H20, a vacuum effect is created and you’re forced to suck unfiltered air from gaps in the mask.

This is something to be aware of if you’re pairing the shop towels with something else.

For example, if you want to use the towels with 2 layers of quilting cotton, it would increase the pressure drop by 6.49 mm H20. The total pressure drop would then be over 15 mm H20, making it hard to breathe through.

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Are blue shop towels safe for masks?

Toolbox blue shop towels being used to clean dirty hands — Photo credit: Sellars.

Do shop towels have toxic chemicals in them?

In the Q&A section of Home Depot, a customer asked “are there any chemicals or fiberglass used in the making of these towels that would [be] harmful if breathed through?”

On 21 April 2020, the Sellars Product Expert replied (note: Sellars is the company that owns Toolbox):

“No, there are no chemicals or fiberglass in the shop towels. Our product is used for cleaning purposes, it’s not meant for PPE use or making PPE items. We do not recommend or advise anyone to utilize our product to make or for use as PPE (face masks).”
Sellars Product Expert. Source: https://www.homedepot.com/p/TOOLBOX-Blue-Shop-Towels-200-Count-Box-6-Boxes-per-Case-55202/205218066 [published: 21 April 2020]

On 15 April 2020 they told another customer:

“The Shop Towels contain no harmful chemicals and are safe for kitchen use.”
Sellars Product Expert. Source: https://www.homedepot.com/p/TOOLBOX-Blue-Shop-Towels-200-Count-Box-6-Boxes-per-Case-55202/205218066 [published: 15 April 2020]

Scary safety warning from Walmart

Walmart safety warning on Toolbox blue shop towels page

Walmart doesn’t seem to agree with Sellars’ claims.

Here’s the warning they have on their Toolbox shop towel page:

“WARNING: This product contains chemicals known to the State of California to cause cancer and/or birth defects or other reproductive harm www.p65warnings.ca.gov”
Walmart. Source: https://www.walmart.com/ip/Toolbox-5440030-Blue-Shop-Towels-55-Ct-Roll-Quantity-1/46651076 [accessed: 8 August 2020]

Unfortunately, they aren’t specific about what chemical, so I had trouble finding what they’re referring to.

Also, the safety data sheet from Sellars says the opposite:

“· California Proposition 65:
· Chemicals known to cause cancer:
Does not contain any ingredients above safe harbor limits.”
Sellars ‘Safety Data Sheet (SDS)’ page 6. Source: https://www.sellarscompany.com/product/toolbox-z400-shop-towels-center-pull-box [reviewed on 03/11/2020]

The closest thing I could find on the p65warnings website was wood dust. Toolbox shop towels are made of 80 to 90% wood fibers, according to their safety data sheet.

I’m still not sure what risk this poses to people.

The p65warnings website says “exposure to wood dust in significant amounts on a recurring basis can cause cancers of the nose, throat and sinuses.”

I have emailed Sellars about Walmart’s warning. I’ll update this post when they reply.

Walmart have a similar warning on their Scott’s shop towel page:

“WARNING: Cancer and Reproductive harm. See www.P65Warnings.ca.gov”
Walmart. Source: https://www.walmart.com/ip/Scott-Blue-Shop-Towels-in-a-Box-200-Sheets/691019537 [accessed: 8 August 2020]

I have emailed Scott’s parent company, Kimberly Clark, for their response.

Are shop towels washable and reusable?

screenshot of conversation about washability of Toolbox blue shop towels

According to a Sellars representative on Home Depot (in the Q&A section), shop towels are disposable and cannot be washed.