High Efficiency Filters, Not Vents or One-Way Valves


According to the United State’s Center for Disease Control and Prevention (CDC), masks with one-way vents or valves do not help to stop the spread of COVID-19. Some users have asked us if Totobobo masks use these vents.

We would like to clarify that Totobobo masks do not have one-way vents or valves (complying with the CDC’s recommendations). Rather, they are actually fitted with replaceable filters (F92, F94, F96, or PRO99) which provide two-way high efficiency filtration of viruses, bacteria, and particulate matter.

These filters are also engineered to accommodate a low airflow resistance to help users breathe easily in them. The remainder of the Totobobo mask contains a soft, transparent, and silver-embedded plastic designed to resist viral and bacterial growth.  

Altogether, this combination of features built into the Totobobo mask and filters provides users with comfortable long-term use and optimal safety for themselves and those around them.

Test reports of the Totobobo filters:

How to perform a seal check with the water mark method?

The protection of a respiratory mask depends on two factors:
1. How good is the air filter and
2. How well the mask is able to seal your face, such that the air you breathe in must go through the filters.

The filters can be tested by reputable laboratory where certified reports are produced. We sent filters to Nelson Labs in USA and the results are published.
However, it is not at all easy for individual user to determine if the mask is really fitting the face completely without any gaps. Totobobo is the only mask in the market provides a simple method, or the “Water Mark check”, to let users ensure the face seal.

Water mark shows poor and good seal before and after ReShape of Totobobo mask.

Water mark shows poor and good seal before and after ReShape of Totobobo mask.

The frost edge of the mask changes to transparent when it touches wet skin. This is called the “water mark”. Followings show a step by step approach to check the seal with the water mark:
– Apply a thin layer of water on the user’s face with cotton wool, especially around the nose bridge and chin area.
– Don the mask and carefully examine the water mark.
– Check if the water mark form a complete, continuous loop encircling the nose, mouth and under the chin, that indicates the mask is making a good seal around your face. The mask is now ready for use.
– If there are patch(s) of frost area breaking up the water-mark-loop, that indicates where the seal breaks and you may need to adjust the mask to improve the seal. There are several things you can do, such as:
1) Adjust the position of the mask. (shift it up and down to find the optimal position)
2) Adjust the tension of the elastic straps (it should be firm, but not too tight)
3) ReShape the mask (use 70°C water or hair dryer, but don’t overheat!)
4) Cut the mask smaller (only when it is really necessary!)

Your mask is ready to give you the best protection when you have a good seal. Do use the water mark method to double check the seal.

How is it possible to filter out sub-micron particles?

This question is repeatedly asked:

How is it possible for Totobobo filters to filter out sub-micron particles?

This is an important question because sub-micron particles ( eg.PM2.5 ) contained in polluted air is the major health concern. The secret of Totobobo filters is the high intensity static charges on each fiber which made up the filter matrix. When you breathe in, airborne particles follow the air and pass through the filter matrix. Fine particles are very susceptive to the static charges and therefore most of them eventually are attracted onto the filter fibers. In fact, Nelson Lab test shows Totobobo F96 filter is able to cut down 99.86% of 0.1 microns particles. Under a microscope it shows how small particles are attached to the filter fibers.


Fig. 1  Fine particles, size range from tenths of microns down to 0.1 microns are attracted to the fibers as they pass through the complex matrix of the Totobobo filter.


Fig. 2 100X magnification view of a needle (0.6mm thickness) and filter fiber.

Totobobo filter with a needle of 0.6mm thickness

Fig. 3    Totobobo filter with a needle of 0.6mm thickness


Quoted from the NIOSH Science Blog below:

N95 Respirators and Surgical Masks

How do filters collect particles?

These capture, or filtration mechanisms is described as follows:

Diagram illustrating the filtration mechanisms of inertial impaction, interception, diffusion, and electrostatic attraction. In each case, fibers are shown filtering particles.

  • Inertial impaction: With this mechanism, particles having too much inertia due to size or mass cannot follow the airstream as it is diverted around a filter fiber. This mechanism is responsible for collecting larger particles.
  • Interception: As particles pass close to a filter fiber, they may be intercepted by the fiber. Again, this mechanism is responsible for collecting larger particles.
  • Diffusion: Small particles are constantly bombarded by air molecules, which cause them to deviate from the airstream and come into contact with a filter fiber. This mechanism is responsible for collecting smaller particles.
  • Electrostatic attraction: Oppositely charged particles are attracted to a charged fiber. This collection mechanism does not favor a certain particle size.

In all cases, once a particle comes into contact with a filter fiber, it is removed from the airstream and strongly held by molecular attractive forces. It is very difficult for such particles to be removed once they are collected. As seen in Figure 2, there is a particle size at which none of the “mechanical” collection mechanisms (interception, impaction, or diffusion) is particularly effective. This “most penetrating particle size” (MPPS) marks the best point at which to measure filter performance. If the filter demonstrates a high level of performance at the MPPS, then particles both smaller AND larger will be collected with even higher performance.

This is perhaps the most misunderstood aspect of filter performance and bears repeating. Filters do NOT act as sieves. One of the best tests of a filter’s performance involves measuring particle collection at its most penetrating particle size, which ensures better performance for larger and smaller particles. Further, the filter’s collection efficiency is a function of the size of the particles, and is not dependent on whether they are bio aerosols or inert particles.

Graph showing a filter's efficiency on the Y-axis and particle diameter in microns along the X-axis. Efficiency falls in the 'Diffusion and Interception Regime'.

There is a large gap around the filter holder! (2014 design)

Some user feedback that the filter holder of the 2014 new design is not as tightly seal as the old design. There is a large gap around the filter holder and the filter inside is clearly exposed. (pic. 1)

Does this gap cause a problem with the seal?

Does this gap cause a problem with the seal?

First the large gap around the filter holder is our design intent. It is designed to allow more air to go through the filter. More air opening means lower resistance and easier breathing. This is an important benefit relates to the comfort of mask wearing.
Now, does this large gap also indicates the new 2014 model is less protective?
Certainly NOT. To understand, you need to check the inside of the mask (pic. 2) Here you can see clearly, all the air has to go through the opening. The seal is valid, as long as the filter makes good contact with the edge of the opening.

The seal is good , as long as the inside of the filter is properly fitted.

The seal is good , as long as the inside of the filter is properly fitted.

To demonstrate the above is true, we use a TSI PortaCount device to perform a fit test of a user using the 2014 new design. The overall fit-factor in this case is 165, clearly above the pass rating of 100.

Fit test result from one of the 2014 design users.

Fit test result from one of the 2014 design users.

Not getting a good fit? “ReShape” your Totobobo mask to get the perfect fit!

Heat moulded Totobobo mask

Heat moulded Totobobo mask

[Click here if you cannot view youtube from China]

Some users feedback that it would be nice to add a nose clip to Totobobo mask, especially for people with prominent nose feature. These users experienced a small gap next to their nose bridge. Many disposable masks comes with an integrated metal nose clip. You can use it to force the mask to “clip” your nose, this is useful to eliminate the small gaps next to the nose bridge. However metal nose clip is not a reliable long term solution for a reusable mask. Our tests have shown that after a limited times of bending, the metal clip will become fatigued and easily broken.

The following video shows how to use  hot water (70°C max.) to mould a Totobobo mask, then use another bowl of cold water to freeze the new shape. This process can be repeated many times and therefore is a better long term solution than a metal nose clip.

The heat treatment can be applied to any parts of the mask (e.g. the chin). The possibilities are limitless. You may need to try moulding the mask several times to achieve the best fit.

“moulding” feature helps to improve protection and wearing comfort.

Better face fit = fewer gaps = better protection
PM2.5, the very fine airborne particles smaller than 2.5 microns that can be inhaled and travel deep into the lungs and enter the blood stream, causes micro inflammation and hardens the blood vessels. Recent studies discovered PM2.5 not only triggers lung and other diseases along the respiratory track, but also triggers cardiovascular diseases and strokes. Common surgical masks or even a poor fitting N95 mask won’t be much help, because airborne viruses or fine particles like PM2.5 can easily bypass the filter through the air gaps. Ensuring face fit is the first fundamental step towards respiratory protection.

Totobobo masks provides three key features to help you to obtain the optimal face fit and protection:

1) Sizing: Totobobo mask is the first and only mask that allows the user to cut to size. You don’t have to risk over cutting your mask. Download this template and test the size with a paper dummy first, before cutting the real mask!

2) Fine tuning with heat moulding: The heat moulding process makes it possible for you to fine tune the face-fitting of the mask. A small gap around the nose bridge or below the chin? No problem, just re-mould the mask and you can eliminate or at least minimize the gaps. You can re-mould the mask as many times as you want. Remember don’t treat the mask with boiling water or you may destroy the mask! Use hot water around 80C instead.

Another point to note, a small gap occurs during exhaling does not affect the effectiveness of protection, and the leak can be beneficial because it helps to release the exhaust air. What you need to check is whether the seal is closed when you inhale, due to the negative pressure while inhaling. Ideally you would adjust the straps so that there are small gaps to speed up the exhaling due to the pressure.

3) Visual seal check: through the unique transparent mask you can check if the mask is touching the chin below and forming a good seal. If the seal is not optimal, you can fine tune the cut, the moulding or simply adjust the position and tension of the strap to get a better fit.

Wearing comfort

If a mask is not comfortable to wear, it won’t get used much and it won’t get much chance to function either.

The heat moulding process can make the mask follow your face profile closely. Therefore you can reduce the tension of the straps while still getting a good fit. Ideally you can adjust the tension to a minimum level to keep the mask on your face. When you exhale, the internal pressure pushes the mask outwards a bit and breaks the seal around the face, quickly releasing the exhaust. When you inhale the mask “sucks” to your face due to the negative pressure and the elastic strap, closing up the gaps and letting the air in only through the filters. The entire mask functions like a one-way valve, but without a physical valve. Some users describe this state as “The mask is breathing with me.”

Got a question? leave a comment or send your question to totobobomask(at)gmail.com




Advanced features of Totobobo mask

Totobobo simulator (free download)