Last January, when I wrote my post about Mask Science with the science behind masks, advantages and disadvantages of mask types, practical tests, tips for optimization and a note on why and how we double mask, I still hoped that the vaccine might make masks redundant in everyday life, and that this could be my last mask post. Right now, it looks like thanks to new variants, masks will stay with us for a while (…), and as many people are looking to upgrade their masks these days, I’d like to explain our double masking with the Hybrid Cloth Mask (aka Luckhaus Mask) in detail.
Table of Contents
Introduction, and Reasons for Double Masking: How Double Masks can combine efficient Filtering and gapless Fit
Double Masking with the Hybrid Cloth Mask on top of N95, KN95 or FFP2 Masks, Surgical Masks and Filter Materials
Material Chart, Frequently Asked Questions, Tipps & Tricks for Double Masking, Conditions of Use and Thanksgiving
Double Masking can combine efficient Filtering and gapless Fit
When in spring 2020, N95 and FFP2 / N95 masks were in short supply even for medical professionals, so that they often had to make them last for weeks, I helped lots of doctors and nurses to sew masks based on my Hybrid Pattern as covers for their precious medical masks, and I was surprised how perfectly the Hybrid fitted on top of them!
Clapp et al found that medical masks filter less than 40% with loose fit, but more than 80% with gapless fit, which shows (a) the filter powers of certified materials and (b) the importance of a gapless fit to actually benefit from these.
With risk group in the family, we have to be particularly careful about protecting ourselves, and the usual FFP2 / N95 masks unfortunately gape quite badly on all of us. Therefore, we’ve also started wearing Hybrid Masks as covers over our FFP2 / N95 masks very early on. Our top masks do not only reliably seal the FFP2 / N95 masks gapless, which we consider of highest importance, but also protect them from getting dirty, so that they can be worn a little longer.
The Hybrid Mask is also very suitable as a top mask for bearded people, because when the side channels are tightly drawn, they press protruding cheek hair much closer to the face, which drastically reduces the usual “beard gaps”.
A very broad variety of Hybrid Mask sewing patterns I’ve created by request for special face shapes, needs and preferences (f.e. noses, beards, space, etc.), which can also be worn as top masks and eliminate (or at least offset) all sorts of issues with the fit of medical masks, can be found in a separate post about Customized Hybrid Mask.
If you are not sure if double masking may be a good solution for you, my post about Mask Science should help to make up your mind and possibly find other ways (f.e. braces) to solve fit issues. There, I introduce the scientific principles behind masks, the problem with gaps, advantages and disadvantages of the mask types, some practical home tests for both fit and filter efficiency, and also a wide range of tips and tricks for the optimization of all sorts of masks! ➔
Double Masking with Cloth Masks over FFP2 / N95 / KN95 Masks
Due to a high material density and increased breathing resistance, FFP2 / N95 masks are particularly sensitive to gaps, i.e. the air passes through where it’s easiest. Therefore, even small gaps can reduce the filter efficiency of FFP2 / N95 masks drastically. To ensure that FFP3 / N100 or FFP2 / N95 masks are worn correctly and fit perfectly on the person wearing them, professional environments (e.g. hospital) annually carry out elaborate fit tests with their employees.
Unfortunately, it’s not possible to replicate such fit tests at home, but there are some simpler tests which let you at least roughly determine how gaplessly your mask fits, and whether there is a need for optimization. For example, if your glasses fog up when wearing a mask, or if you can see or feel air flow around the mask’s edges, this indicates leakage!
FFP2 / N95 masks are characterized by a very high filter efficiency, but also have increased breathing resistance. Cloth masks worn on top of them should therefore be very thin, so that gaps are reliably sealed, but breathing is not made even more difficult. Please test not only the fit of your mask combos in advance, but also whether you can breathe easily with both masks, f.e. when climbing stairs! If this doesn’t work out well for you, please do not use a top mask.
In general, it is advised to wear FFP2 / N95 masks for a maximum of 75 minutes at a time, then to give yourself a rest for at least 30 minutes, and to never wear the masks for more than a total of 8 hours when re-using them.
The Hybrid Cloth Mask on Top of FFP2 / N95 / KN95 Respirator Masks
The shape of the Hybrid Mask complements the usual coffee-filter-shaped type of FFP2 / N95 masks surprisingly well, and even the angles match each other! Over the standard one-size FFP2 / N95 mask, the Hybrid Cloth Mask in length L (print the pattern in 110%) and width M (print the template in 100%) fits perfectly on most people. For example, my family’s cloth mask sizes range between S and L, but as a FFP2 / N95 cover mask, L/M fits all of us gaplessly.
In everyday life, we usually wear two-layer top masks, which I have sewn in combinations of 80 gsm NWPP (non-woven polypropylene) and light, breathable cotton, such as shirting. Breathing with a double mask is of course a little harder than without, but we find it absolutely tolerable – and it is even possible to teach several hours per day with it!
The Hybrid Cloth Mask can also be sewn in a single layer, by adding 1-2 cm at top and bottom, folding this allowance twice to the inside and stitching it down, while leaving open 1-2 cm at the side of the top seam, for nose wire insertion.
In the appendix of recent versions of the pattern and instruction PDF for my Hybrid Cloth Mask, you’ll find special cover patterns in length L / width M, for multiple layers as well as lengthened and marked for a single layer of fabric.
Before donning the FFP2 / N95 mask, roll the flat-folded top edge around a finger, so that the wire won’t peak over the nose. When the mask is on your face, the top can be pulled down slightly, and if the mask is too large, the bottom edge can be folded inwards. To achieve your best fit with a top mask, I recommend testing (a) different height levels (on some, FFP2 / N85s show at the sides of the top, while on others, they don’t), and (b) with and without nose wire.
For one-layer and two-layer Hybrid Cloth Masks, sewing a 20 x 3 cm / 8” x 1,2” strip of pellon into the inside of the top, aligned with the cutting edge, can help the nose wire to fit softer, which on some wearers might even improve the seal.
Double Masking with Cloth Masks over Surgical Masks
Surgical or procedure masks are made of highly efficient filtering materials, but due to loose fit (due to construction as source control, to keep wearer’s droplets from spraying, and not to protect them from aerosols!), a lot of their initial filter efficiency gets lost. The filter efficiency can therefore be drastically increased when surgical masks are made to seal gapless, i.e. from less than 40% for a loosely fitting surgical mask to over 80% for a gaplessly fitting surgical mask.
If you would like to have more space behind your masks and / or hide the surgical mask as well as possible, you can simply knot the ties of the surgical mask on the sides, as close as possible to their base, and fold in the protruding material. Due to these knots, the surgical mask protrudes further forward, so that breathing becomes even easier.
The Hybrid Cloth Mask on top of Surgical Masks
To be worn over surgical masks, the Hybrid Cloth Mask can be customized into any individual size (my pattern is available in XXS to XXL, and there are also Customized Patterns for various shapes and needs such as glasses, noses, beards, kids, space, etc.!). The combo usually fits gaplessly, is easy to breathe in and reliably stays in place, and we actually find it more comfortable than wearing a loosely fitted surgical mask without a Hybrid Mask on top :)
We usually wear two-layer or three-layer top masks, which I have sewn in combinations of NWPP (non-woven polypropylene), polycotton, cotton, pellon and / or silk, over surgical masks. In contrast to FFP2 / KN95 top masks, I tend to make sure that the materials I use have decent filter properties, to increase filter efficiency a little. As with FFP2 / N95 face masks, it is very important to test in advance whether you can breathe without any problems!
Besides my Hybrid Pleated Mask, my brandnew Hybrid Boxy Mask fits really well over surgical masks too. The Hybrid Boxy Mask offers even more space and can easily be sewn in more layers than the Hybrid Pleated Mask, but due to a rather solid form, it is slightly less versatile and doesn’t match FFP2 / N95 masks as well as the Pleated.
For single and double ply masks, sewing an 8″ x 1″ strip of batting such as Pellon into the inside of the very top part, right between top seam and nose wire seam, can help the nose piece to fit a bit softer and thereby, seal even better.
High Filtration Materials for Inserts or Double Masks
As mentioned before, we have a medical mask mandate in Germany, and furthermore, we can’t buy high filtration materials such as Halyard or Filti, so we don’t have a choice but to double with or insert precut medical masks.
If you live in a place where cloth masks are allowed and high filtration materials are available, you can not only either (a) sew the filter materials into your mask or (b) use them as a separate insert, but you can also (c) sew or staple your own filter masks from high filtration materials. Alternatively, you can precut medical masks and use them as a filter.
The Problem with Sewn-in Filter Materials
The easiest option would be to use filter materials like a layer of fabric and sew it right into your reusable cloth masks. Unfortunately, decent filter materials (such als Filti) loose most of their filter efficiency (> 65%) through washing (< 20%), while materials such as NWPP are washable and reusable, but not as efficent (> 40%) to begin with.
Sewn-in filters reliably stay in place, but are impossible to separate, so you can’t care for the two kinds of materials the way they need to be cared for. Ideally, fabrics should be washed, while filters can often be reused, but should be disposed at the end of their pre-detemined lifespan. With separate parts, you can keep reusing the cloth mask.
If for some reason sewn-in filters are the only option you (or the person your are sewing for) are willing to wear, I’d recommed to at least go with as many layers of NWPP (f.e. 2-3 layers of 80 gsm) as the wearer still finds breathable.
The Hybrid Cloth Mask with a Filter Frame on the Inside
Filter inserts have the advantage of separate parts that can be cared for as recommended, and they’re easier to use, because unlike double masks, they require only a single pair of ties. On the other hand, inserting filters through a small opening can be fiddly, the surface usually isn’t covered completely, and the insert doesn’t reliably stay in place.
Extra pockets often don’t cover the whole surface either, some even make breathing harder without added filtration.
A new solution I’ve found for fiddly inserts are Filter Frames, i.e. the mask is cut larger and folded inwards at top, bottom and sides, so the precut filter material can be placed on the inside of the mask (instead of in between!). This makes is easier to cover the entire surface, and faster to distribute filter material into corners and pleats. The inner frame holds filters securely in place, all the way around! You can find instructions and pattern in a separate post. ➔
The Hybrid Cloth Mask on top of Hybrid Instant Masks
Compared to filter inserts, double masking is far less fiddly, and bottom masks stay in place better than inserts.
In addition to the Hybrid Cloth Mask, I have created a simplified Hybrid Instant Mask (originally for non-sewers :)) that is based on the very same pattern and can be sewn (or even stapled!) extremely quick and easy. Those two masks fit gaplessly, comfortably, breathable and slip-free on top of each other, and complement each other perfectly! ➔
Our Double Masking Choices in a Chart
After being asked about this a couple of times, here’s a little chart of the choices me and my family are making.
For (a) High Risk Situations, we wear certified FFP2 / N95 masks sealed gaplessly by 1-2 ply Hybrid Cover Masks, for (b) Mid Risk, we may choose certified surgical masks knotted by the sides then sealed gaplessly by 2-3 ply Hybrid Pleated or Boxy Masks, and for (c) Low Risk, we may wear 3-4 ply NWPP Hybrid Pleated or Boxy Masks on their own. Filti batches highly vary in efficiency, but if was available in Germany, we might use it for Mid to Low Risk Situations.
|Risk||Mask / Filter||With Gap||No Gap||Seal gapless with Hybrid||Layers||Material⁶|
|High||FFP2 / N95¹||< 35%²||> 95%¹||Cover (= Pleated L/M)||1-2||NWPP / Cotton|
|Mid||Surgical¹||< 40%³||> 80%³ / > 95%¹||Pleated / Boxy||2-3||NWPP / Cotton|
|Low||Filti||N/A||< 20%⁵ / > 65%⁴||Pleated / Boxy + Frames||2-3||NWPP / Cotton|
¹ Approved by CE (EU) or NIOSH for submicron particle filtration with ~0.3 μm / ASTM for bacterial filtration with ~3.0 μm (US); specs see Makermask, locations see 3M, ² Konda et al (corrected for methodological errors!), ³ Clapp et al, ⁴ Hao et al, ⁵ Bement et al, ⁶ For top masks, we use NWPP with shirting inside. Test in advance if you can breathe well!
For comparison, I meant to show the average filter efficiency of material combinations used by makers, but studies have very different test settings and materials involved, plus results vary so much that they’re hardly predictable.
When looking at individual material studies, I recommend to not only check (a) filtration efficiency (higher is better), but also the particle size tested! For example, surgical masks are tested by ASTM standards for bacterial filtration at 3.0 μm, while N95 are tested by NIOSH standards for submicron particle filtration at 0.3 μm. Both test for at least 95% efficiency, but as bigger particles are easier to filter, standards set for N95s are far higher. Furthermore, most studies show (b) breathability of materials, as differential pressure (lower is better) or ASTM level (higher is better). If indicated, (c) fluid resistance (higher is better) can tell you if a material blocks splashes and sprays!
In terms of filtering and breathability, fabric can’t really compete with materials used for medical masks, and as more infectuous virus variants are spreading, I advise against wearing low filtration masks in high risk situations. Cloth masks make great top masks though – f.e. to seal surgical masks gapless and thereby, double their filter efficiency!
Frequently Asked Questions, Tips and Tricks for Double Masking
These tipps and tricks do not only relate to one of the combos introduced above – the Hybrid Cloth Mask on top of N95, KN95 or FFP2 type of Masks, Surgical Masks or Homemade Filter Masks –, but to any type of double masks.
What’s the best way to tie Double Masks?
So far, all our FFP2 / N95 and surgical masks have had extremely long ear loops. We either (a) add a slip knot to the extended ear loops, so that they can be used just like short ear loops and prevent the mask from slipping, or (b) attach the extended ear loops behind the head with the small hook, which is often included, a paper clip or a hair clip.
On top, we wear the Hybrid Mask either (a) with adjustable ear loops made of soft, flat elastics or, for longer wearing, (b) with extended ear loops that can be attached ar the back of the head together with those of the FFP2 / N95 or surgical mask (see below), or (c) very long head ties made of jersey strips, also known as tshirt yarn. On me, head ties fit best when I cross them, so that the bottom tie sits above my hair bun and the top tie sits under the hair bun.
In less risky situations, where you have to don and doff masks more often, we treat both masks as one. To do this, we set the length of the ear loops of the top mask to the length of the ear loops of the bottom mask, pull the knot tight and down or into the channel, and nest the masks into each other. Now we slide a paper clip (if hair gets tangled, you can bend them open! :)) over both loops on the right side, until they sit safely in the large hole of the paper clip.
When donning the mask, we check that both masks are centered and that the reverse pleat of the top mask sits over the top edge of the bottom mask. Then, behind the head, we hook the paper clip into the two left straps. It doesn’t take any longer and is not more complicated than donning a single mask and, if necessary, can be done one-handed!
In general, tying masks behind the head is recommended, as it offers a more secure fit. With headbands or behind the head ties, masks can be pulled much tighter (which means more gapless!) without giving any discomfort to the ears.
How do you carry and clean double masks, and do you reuse them?
We usually carry our masks readily doubled and folded in the middle, in small plastic bags that we wash regularly. If the masks are definitely not contaminated, dirty or wet after being worn, we will likely wear them again. After use, we put all our masks in paper bags, then wash the cloth masks in the laundry, and if the high filtering masks are still perfectly clean and dry, we might wear them again after 2-3 weeks of airing, and a maximum of 8 hours in total.
Can I double mask the other way, Filter Mask over Cloth Mask?
Of course you can, but you might end up corrupting the medical mask’s filter efficiency, so I highly recommend to wear the medical mask as close to your skin as your possibly can, and the cloth mask on top! Plus, when your medical mask stays clean (and it will rather get contaminated on the outside than on the inside), you can use it a little longer.
Doesn’t the CDC recommend to not use top masks over KN95s?
The CDC doesn’t recommend double masking with the KN95 type of masks in general, but doesn’t give reasons for that. As far as we could figure out, they might (a) assume KN95s to fit perfectly on everyone (which made us assume that they’re likely all 1.80 m / 6 ft and male, as that’s the usual standard for product testing :)) and (b) want to avoid people to put 5 layer homemade masks on top of high filtration masks, as this might result in serious breathing issues.
From a common sense perspective, when KN95s just don’t fit at all (and therefore, might loose most of their filter efficiency!), the best you can do is find a way to make them fit gapless – and if done responsibly, with a thin layer or two, top masks are the most reasonable option I know. But in case you can’t breathe well, please don’t double mask!
What can I do when I have trouble breathing with double masks?
In addition to Double Masks that fully cover the front part of the mask, there is also the option of wearing a mask frame that is open at the front, and therefore does not further restrict the breathability of the N95 or surgical masks in any way. For this purpose, I created the Hybrid Mask Frame that you can sew yourself and which thanks to a reverse nose pleat does not even need a nose wire to seal ill-fitting N95/KN95 masks gapless, without any fogging or slipping. ➔
Can I avoid all the plastic waste from medical masks?
I don’t like that either, and I wish there was a way to keep me and my family safe without producing that much plastic waste! Unfortunately, the materials you can buy for sewing homemade masks just aren’t as effective at filtering, while medical masks are. With top masks, you can at least keep the disposables a little longer, and then safely reuse them.
Is Double Masking allowed in Germany?
Last January, it was decided that medical masks should be compulsory, not visible medical masks (that would hardly be scientifically justifiable!) – so, as far as I can tell, there is nothing wrong with a sealing cloth cover on top.
If anyone complains that my mask combo doesn’t look like a medical mask (which hasn’t happened yet, maybe because my top masks are made from NWPP :)), I refer to double ties and have practiced flipping one side of the top mask for a moment so that the undermask stays in place! I usually have the packaging with me too.
Where can I find the printable pattern for the Hybrid Mask?
Pattern and instructions for the Hybrid Mask, which we are using to seal all our certified medical masks gapless, can be found in a separate post. I very recently added Hybrid Cover patterns in height L / width M (fits perfectly over the standard one-size of FFP2 / N95 / KN95 type of masks) for single as well as for multiple layers to the attached PDF! ➔
There’s also a very detailed picture tutorial, patterns and instructions for filter frames to make insertion of filter materials easier and safer, custom patterns for a wide range of face shapes (incl. nose, chin or beard) and the most recent addition of a Hybrid Boxy Mask, which offers an abundance of space, with pattern, instructions and pictorial.
Can I possibly purchase the Hybrid Cloth mask from you?
Right now, I only sew for friends and family, because it seems more important to publish instructions and pattern of my Hybrid Cloth Mask, in order help others to help those in need – and besides my daily work, there’s no time for more than answering questions and continously updating German and English posts and instructions. But in the meantime, I’ve been lucky to find fabulous sewing partners, who offer professionally sewn, beautiful Hybrid Masks! ➔
This post corresponds to my personal level of knowledge by January 14th, 2022. When there is any new information to add or to correct, I revise accordingly. I am always happy to receive your comments, questions, tips and studies!
If you are curious now and would like to read more about Hybrid Cloth Mask Pattern, associated Pictorial Instructions, Instant Masks, Tying Techniques, etc., all links with pictures are available on my brandnew Mask Hub Page! ➔
Conditions of Use, Rights and Sharing
This post is more than welcome to be shared. Design, pattern and instructions of the hybrid mask are, however, protected by German copyright laws (© Iris Luckhaus | All rights reserved) and may only be used non-commercially. I’m always delighted to discover photos of hybrid masks with the tags @irisluckhaus and #luckhausmask! :)
For updates and further developments (which are sure to come!), please follow me on Facebook, Twitter, Instagram, Xing, LinkedIn, Pinterest or YouTube. If you’d like to share my pattern with your friends, feel free to use my posts!
I’m spending a lot of unpaid time on elaborating and explaining those instructions, helping the helpers to help. If you’d like to encourage this, I’d highly appreciate if you could buy me a little time via Paypal (firstname.lastname@example.org)!
If you’d like to use my instructions commercially (i.e. with the intention of making a profit), f.e. by selling masks sewn according to my pattern, please contact me and let me know more about your business, your location and your ideas!
Great thanks to my favorite mask testers Matthias Klesse, Angelika Luckhaus and Reinhard Luckhaus as well as to several amazing, science-oriented makers I’ve met in Facebook groups, Rebecca Ma Lau, Devon Ostrom, Dr. Jocelyn Songer, Eugene Dysiatnik, Ania Mitros and Paul Hammant, for instructive discussions, interesting studies, good questions, great enthusiasm and exciting tests, for reading and feeding this post – and the amazing encouragement!