Testing 9 types of air filters with a laser particle counter

The filter is the most important component of a respirator. The quality of air that gets into your lung is determined by the quality of the filter, provided there is a good seal between the mask and your face.

The design of Totobobo mask makes it quite easy to replace the filter with any flat, air permeable material. It is tempting to use a “filter look-a-like” such as cotton wool or a piece of felt to replace the used filters. Does it work? I am interested to find out how effective these different alternatives are.

A Dylos laser particle counter is used to collect objective data. The particle counter is affordable and performs consistently. I’m using the Pro version which is able to detect two fine particle sizes: 0.5 and 2.5 microns. The particle counter has an air-inlet and a exhaust vent. Air drawn into the counter goes through a passage and there is a laser diode and an optical counter along the air passage. If the air inlet is covered by a piece of filter, air drawn into the unit will be filtered and therefore produce a lower particle count reading. The performance of the filter can be calculated by dividing the ambient particle count value with the “filtered” value. For example, if the particle count drops to half, the protection factor of that particular filter is 2.

Laser Particle Counter

Dylos Laser Particle Counter

The method is simple and easy to understand. First of all the ambient particle counts is measured against two different particle sizes – 0.5 microns and 2.5 microns. Different types of “filters” are used to cover the air inlet (edge seal with tapes) one after another. Reading of each filter is obtained after 2 minutes when the value stabilized. Finally, the ambient particle count is once again measured without any filters. The first reading without the filter and the last reading are within 5% tolerance.

Laser Particle Counter reading without filter

Laser Particle Counter reading without filter

Protection factor (P) of each filter is calculated by the formula:

P = Qi / Qn

Where Qi is the value of ambient particle count without filters and Qn is the particle count of the filter concerned. Higher P value indicates better protection factor.

The Totobobo filter (low cost anti-pollution filter) produces a high protection factor of 5564/587 = 9.5 (for 0.5 microns) and 184/10 = 18.4 (for 2.5 microns). This figure indicates a high filtration efficiency of over 90%, effectively raise air quality from “VERY POOR” to “FAIR”.

Totobobo mask filter test

test reading of Totobobo filter

Surgical mask is commonly used, the problem is getting a good seal. In this test, we seal the surgical mask filter media over the inlet to measure the filter effectiveness. As expected the protection value is not very high: P=2.9 for 0.5 microns, P=4.8 for 2.5 microns.

surgical mask filter test

test reading of surgical mask filter

As a reference, the filter of a Respro City mask is also tested. The result is disappointingly poor: P=2.2 for 0.5 microns, P=3.1 for 2.5 microns. I am shocked since this product was reported some years ago to be among the “top performers”. I checked several times to make sure the readings are correct. It may be possible that my sample is dated (over a year old). I will update this record if new evident is found to prove this results wrong.

Respro City mask filter test

test reading of City mask filter

Magiclean is cheap and commonly available and it’s working principle is based on static charge in the fibre, a characteristic of Totobobo filter. I expect it shell produce reasonable good performance. However, the result of 4 layers of Magiclean wiper is the worst out of the lot: P= 1.6 for 0.5 microns, P=2.2 for 2.5 microns.

Magiclean dry wiper sheet test

test reading of Magiclean dry wiper sheet

Facial pad is probably the most commonly used “replacement filter” since some of them available in similar dimension as Totobobo filter. The result of the test is: P=2.4 for 0.5 micron, P=3.5 for 2.5 micron. This is slightly better than the result from the Respro filter.

Facial pads test

test reading of Facial pads

Finally a benchmark test was performed against the well know 3M 8210 N95 filter. However, as the air resistance is too high, we need to enlarge the total surface area and we manage to seal the enlarged area around the inlet. The performance of this filter is remarkable: P=12.8 for 0.5 micron, P=33 for 2.5 micron, highest of the lot. The only problem with this material is the air flow resistant. It is more difficult to breathe through.

Protection factor (higher better)

Totobobo anti-pollution filter
Totobobo 94% filter
Totobobo 96% filter
Surgical mask
Respro City filter
Respro Techno Gold filter
Magiclean wiper
Facial pad
3M 8210 N95 (enlarged area)
0.5 micro
2.5 micro
test results of 9 types of filters

test results of 8 types of filters: higher figure = better performance

Note: these tests are intended to compare relative protection factors between different filters. These test results are not calibrated to various manufacturer’s standard or NIOSH.


3M 8210 N95 and Totobobo are the only two filters provide real protection factor above 9.5. These results is consistent with the finding of a study done in the Chinese University of Hong Kong (Prince of Wales Hospital). However, the air resistance of the 3M 8210 filter is too high and is not suitable to be used with Totobobo mask.
All other alternative filters are considerably less protective.

I managed to get my hands on a new Respro Techno Gold filter and tested it with the laser particle counter. The result is much more promising than the Sport filter. In addition, I also tested the Totobobo 94% and 96% filter to complete the picture. The 94% is the 2nd best performer for 0.5 micron and slightly less protective than the 3M 8210 filter for 2.5 microns. The Totobobo 96% is the best filter so far. Added a chart for easy comparison.

read more :
Cyclist, protect your lung when riding in the city
How to change Totobobo filter?

Low cost Anti-pollution filter

We are excited to introduce a new low cost anti-pollution filters. It provide sub-micron performance targeted at the most dangerous fine particles from traffic pollution (PM2.5 & PM10). It is also extremely effective against wood dust from power sander or wood turning. The filtration efficiency is between 90%~99%.

The filter cost below one dollar a pair, by far the best value in the market. Combining with the well known advantage of Totobobo mask, we are making top notch protection and comfort with extra affordability. We trust that this new filter will help to extend the market reach. According to user’s feedback, we learnt that the cost of the filter is a crucial factor in deciding the long term affordability of a reusable respirator. After all, the mask is only a one time investment. Cost of the filter is the long term issue.

Now for less than 1 dollar a week, everyone can keep the lung clean while enjoying the benefit of cycling, even in the most polluted cities.

This new anti-pollution filters can be purchase from our BUY page immediately.

low cost air filter

30 pairs of anti-pollution filter in zip lock bag

Cost comparison of Totobobo filter with competition:

I Can Breathe

Filter (USD)

Duration (hours)
30 (estimated)

Cost per hour

How serious is the air pollution in Hong Kong?

The air pollution reached a new high on September 24, 2009 in Hong Kong, triggering a warning for people with heart or respiratory illnesses, according to the Hong Kong Environmental Protection Department. I have the impression that the air pollution in Hong Kong is getting worst due to the industrial activities in the nearby southern China, especially the Pearl River delta area. But I have no idea how bad the pollution is. When I am travelling there I feel the air is OK but it is certainly more polluted than Singapore.

Ball pen sketch by Wyser Chu 2009

Hong Kong air pollution

Air pollution causes premature death for thousands of people in Hong Kong each year. It strikes hardest at those who need our care most – children, the elderly and people who are already sick. What happens when you inhale pollutants? Tiny particles (PM2.5, PM10) and gases move deep into the lungs and into your bloodstream. The insides of your lungs can become damaged and inflamed, making it easier for you to get sick. Over time, air pollution can cause permanent changes to your lungs, just like smoking.
Worried about your children breathing dirty air? You have good reason to be. Their lungs are still developing, and since they breathe faster and tend to spend more time outdoors being active, air pollution affects them much more.

According to the Hong Kong Lung Foundation:
– Children living in areas with heavy traffic have more chest problems, such as chest infections and asthma, than those living in cleaner environment;
– During days with high air pollution, more people with asthma, chronic lung diseases or heart diseases have to see their doctors or are admitted to hospital because their disease get worse. Some may even die;
– A small increase in lung cancer risk has also been reported as a result of living in heavily polluted cities;
– Shorter life expectancy of people living in polluted areas compared with those living in cleaner environment by 2 to 3 years.
– Respirable suspended particles (RSP) Causes inflammation of the lungs and airways
– (RSP) Fuel from traffic- Most harmful to health among pollutants, mostly diesel, Construction and road dust. Most harmful to health among pollutants
– Incineration

Dylos laser particle scanner

Dylos laser particle scanner: Nathan Road particle pollution count

Over the last few weeks I brought along a portable laser particle scanner (Dylos). The scanner is able to measure the number of particles of 0.5micron and 2.5 microns. This handy machine allows me to quantify the level of particulate pollution first hand. Air quality rating above 3000 is considered to be very poor, rating below 1000 is good. I was eager to find out if the machine agree with my impression. To be honest, I got a shock the first day. soon after I touch down- the rating on the particle scanner is 10,900 near the west part of Hong Kong island. The normal rating in Singapore is around 1000 to 5000. Over the 10 days I collected data from different part of Hong Kong. The worst rating were obtained along Nathan road (37,000) and Tai-Kok-Tsui (36,000).

The best rating was from Lok-Ma-Zhou (2500), the less busy border between China and Hong Kong. The rating at the Lo Wu station was 10,000. It is necessary to mention that these rating were taking at different days and time, so they should not be taken as an absolute indication for these area.

A day trip (2009-12-22) from Hong Kong to GuangZhou produced an impression of the relative pollution level between the two cities:

Pollution data from Hong Kong to Guang Zhou

Pollution data from Hong Kong to Guang Zhou within a day

@ 7:45 Shek Tong Tsui (Hong Kong Island) 20500
@ 8:50 Sheung Shui (Near border) 26000
@ 10:50 Guang Zhou 30000

It is clear that the pollution level get worst as we approach GuangZhou from Hong Kong.

Anther day trip (2009-12-30) from Hong Kong to Guang Zhou via Shenzhen gave another perspective:

@ 8:35 Shek Tong Tsui (Hong Kong Island) 10000
@ 10:00 Lok-Ma-Zhou (2nd border) 2500
@ 11:15 ShenZhen 8100
@ 18:40 Guang Zhou 17000
@ 20:35 Lu Wu station (1st border) 10000

The air seems to be equally bad from the Hong Kong island all the way up to the Hong Kong/Shenzhen boarder (8100~10000). But interestingly there is an obvious “clean air zone” around the Lok-Ma-Zhou area (2500), which is next to the largest wet land under preservation in Hong Kong.

Lok Ma Chau- better air quality due to large area of wetland

Lok Ma Chau- best air quality in Hong Kong due to large area of wetland

Judging from these data, the pollution level in Hong Kong is indeed worrying. The rating of 10000 to 20000 is 3~6 times the “very poor” indication.
Given that it is a densely populated urban area and it’s proximity to the “factory of the world”, I wonder what can be done to improve the air quality in Hong Kong?

A list of How To’s

Here is a compilation of our How To’s for the Totobobo Mask, if what you’re looking for cannot be found, do not hesitate to drop us an enquiry at totobobomask @ gmail.com


How to ReShape your Totobobo Mask for a perfect fit?

How to perform a seal check with the “Water Mark” Method?

How to wash the Totobobo Mask?

How to customize the Totobobo Small Mask?

How to customize the Totobobo Large Mask?

How to adjust the earloop strap?

How to ReShape your Totobobo Mask for a perfect fit?

Heat moulded Totobobo mask
Heat moulded Totobobo mask

[Click here if you cannot view youtube from China]


Some of our user’s feedback stated that it would be great to add a nose clip to the Totobobo Mask, especially for people with a prominent nose. These users are experiencing small gaps between the mask and their nose’s bridge. However, a nose clip is not a reliable solution in the long run for reusable masks. Prototype testings have showed that the clip breaks or loses it’s rigidity after repetitive bending and will break eventually.

The following video shows how to re-mould the Totobobo Mask, using hot and cold water. The hot water helps to soften the body of the mask, while the cold water helps to harden the mask after reshaping it to the desired shape. This method can be done over and over again, there fore, making it a more reliable solution.

The heat treatment can be applied to any parts of the mask (e.g. the chin), not only the nose area. The possibilities are limitless. You may need to try moulding the mask several times to achieve the best fit.


Moulding feature further enhances protection and comfort for the user.

Better face fitment = lesser gaps = better protection

PM2.5, a very fine airborne particle, is smaller than 2.5 microns which can be inhaled and travel deeply into our lungs, which will then enter our bloodstream. These particles causes micro inflammation and hardens our blood vessels. Recent studies have showed that the PM2.5 not only triggers diseases in our lungs and other respiratory organs, but also triggers cardiovascular diseases and strokes. Common surgical masks or even a poor fitting N95 mask won’t be of much help due to the cunningness of the PM2.5. Ensuring a secured face fit is the first fundamental step towards respiratory protection.

Totobobo Mask have three key features to aid you in obtaining a optimal face fit.

  1. Sizing : Totobobo Mask is the first and only mask that allows its user to cut to fit. You don’t have to risk over cutting the mask. Download this template to test the size using a paper dummy first, before proceeding to cut the actual mask.
  2. Fine tuning with heat moulding : The heat moulding process makes it possible for the user to fine tune the fitment of the mask. Small gaps around the nose or under the chin? No worries! Just re-mould the mask and you’ll be able to eliminate, or at the least, minimize these gaps. You can re-do this step as many times as you like! Remember to not use boiling to re-mould the mask, otherwise you’ll risk destroying the mask. Use warm to hot water around 80C instead.

Another point to note, a small gap occurring during exhalation does not affect the effectiveness of the protection, in fact, it may be beneficial as it helps to release exhaust gases quickly. What you need to check is whether the seal is closed tightly when you inhale, due to the negative pressure while inhaling. Ideally, you should adjust the straps so there there are small gaps to speed up exhaling and feeling comfortable at the same time.

    Visual Seal Check (VSC) : Using the transparent property of the Totobobo Mask, you can check if the mask is touching the areas below the chin, forming a good deal. If the seal is not optimal, you may fine tune the cutting and moulding of the mask, or simple adjusting the position and tension of the strap to get a better fit.

Wearing Comfort

If a mask is not comfortable to wear, the user will use it less often, so the chances of it being functional is generally lesser as well.

The heat moulding adjustment allows the mask to be re adjusted to fit your face profile closely. A good fit is beneficial as it not only provides a good seal, but you’ll also feel more comfortable wearing it and also not forgetting, you can loosen the tension on the straps as well. During exhalation, the internal pressure pushes the mask and forces the seal to be broken, releasing the air quickly. During inhalation, the process creates a “sucking” motion due to the negative pressure, which closes up the gaps, forcing air to enter only by the filters. The Totobobo mask functions like a one-way valve, without it being a valve physically. Some users described it as “The mask is breathing with me.”

Got a question? Leave us a comment or send your questions to totobobomask@gmail.com

How to perform a seal check with the “Water Mark” Method?

The protection a Respiratory mask provides solely depends on two factors:

1: How effective the air filter is

2: How well the mask is able to fit to the user’s face, making sure the air you breathe        in is only passed through from the filters.

The filters are test by reputable laboratories and certified reports are produced.

We have sent files to Nelson Labs in USA and the results were published.

However, it isn’t that easy for users to check if the mask is providing a perfect fit on their face, without any gaps. Totobobo Mask, by far, is the only mask on the market which allows this method to be applied, the “Water Mark Check”.


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 edge of the Totobobo Mask, which is frosted, turns transparent when it comes into contact with wet skin. This is called the “Water Mark”. The following shows a step by step approach on how to check the sealing of the mask using the water mark.

1 : Apply a thin layer of water on the user’s face with cotton wool, mostly around the nose bridge and the chin areas.

2 : Put on the mask and carefully examine the water marks.

3 : Check if the water mark forms a complete, continuous loop, from the nose all the way through the mouth and under the chin. If the water mark forms a complete loop, it indicates that the mask is providing a good seal and fitment around your face. The mask is then ready for use.

4 : If there are segments of frosted markings that breaks the continuous loop, that means the the mask is not sealed perfectly to the user’s face and has gaps in between. You will have to adjust the mask to improve on the sealing of it.

There are several things you can do to improve the sealing of the Totobobo Mask.

  • Adjusting the position of the mask. (Shifting it up and down)
  • Adjusting the tension of the elastic straps. (Firm but not too tight)
  • ReShape the mask (Using Warm but not boiling water and a hairdryer.)
  • Downsize the mask by trimming it down. 

Your mask is ready for use and provides the best protection only if you have a good seal. Do use the water mark method to have a confirmation on the seal!

How to customize the Totobobo Large Mask?

One of the most unique features of the Totobobo Mask is the “Cut to size” feature. The original mask fits most adults except users with smaller faces, for example, women and children.

TOTOBOBO mask can be cut to size

Totobobo Mask is the world’s first customizable respirator. Other products are only available in one size, which only fits a particular age range or facial structure. For many, that is little that can be done to solve this problem. Totobobo Mask, on the other hand, is capable of being trimmed to fit a wide range of faces for optimal comfort and sealing. The mask fits most adults but can also be modified to fit children as young as 5 years old. Totobobo Mask is the most versatile Respirator on the market. Customizing the mask’s size is simple, just follow these steps:

What you need :

A clean pair of sharp scissors

A pair of clean hands

Firstly, you’ll have to determine how small you want the mask to be trimmed to. You can do a quick estimate by covering the mask over the user’s face, or better yet, get a Totobobo Simulator. If you’re uncertain of the exact size, we suggest you to trim the mask down a ring at a time. The mask should ultimately form a snug fit onto the face, but not too tight to hinder the comfort of the user.

Remember to measure twice before you cut.

Then, carefully cut the mask starting from the bottom ring. Follow the markings carefully and slowly cut through the mask. Trim any excess bits and test the size if necessary. The excess material that has been cut out can be disposed and the mask is ready for use.


Step 1 - start the cut from the bottom of the mask
1 – start the cut from the bottom of the mask
Step 2 - insert the scissors into one size of the opening
2 – insert the scissors into one side of the opening

Step 4 - turning around to the other side

6 - almost done
4 – make a loop to the starting point
7 - see! you've got your small mask now
5 – see! you’ve got your small mask now


Test the cut with a Totobobo mask simulator

Buy Totobobo mask

How to customize the Totobobo Small Mask?

Getting a face mask that will fit you perfectly isn’t an easy task. However, with Totobobo Mask, we’re here to make things easier for you!

Our masks are fully customizable, you can cut them down to whatever size you like. Of course, this isn’t an easy thing to do without any guidelines, therefore, we’ve posted this up to help our users have a better insight on how to customize their masks.

Before we proceed, it will be best if you have the Totobobo Mask simulator, it comes together with the product. If you happen to not have one with you, feel free to download it here : Totobobo Mask Simulator

Here is a step by step instruction with photos to guide you :

If the paper mask is too big, cut away the first line near to the chin-edge. Put it on the user's face again to test the size.
If the paper mask is too big, cut away the first line near to the chin-edge. Put it on the user’s face again to test the size.

Continue to cut the mask smaller, and test the size. Line by line until you get the mask size fitting your children.
Continue to cut the mask smaller, and test the size. Line by line until you get the mask size fitting your children.
Here showing the situation after the second line is cut away. Suppose this is the size fitting your children.
Here showing the situation after the second line is cut away. Suppose this is the size fitting your children.
Now insert the paper simulator into the middle of the mask. Try to align the red circle with the filter cover.
Now insert the paper simulator into the middle of the mask. Try to align the red circle with the filter cover.
Use the paper dummy as a guide, cut the mask with a pair of scissors. (The simple scissor shown in the photo is very good for cutting Totobobo mask)
Use the paper dummy as a guide, cut the mask with a pair of scissors. (The simple scissor shown in the photo is very good for cutting Totobobo mask)

The final result: a new Petit mask matching the size of your children. You may still need to ReShape the mask to fine tune the seal. The final result: a new Petite mask matching the size of your children. You may still need to ReShape the mask to fine-tune the seal.

A fitting mask for a happy child!

For further inquiries or assistance, please email us at totobobomask@gmail.com

How to adjust the Totobobo earloop strap?

Wearing a face mask which is too tight or loose can be uncomfortable over a period of time, thankfully with our earloop straps, they are extremely elastic so our users can adjust the length of the straps freely! 

Here are a few steps that you can follow in order to achieve your desired length.

For users who have a bigger head or wearing the mask over any accessories, they may wish to have a longer strap length. 

To do so :

  1. Tie the straps directly across, from the bottom tab to the top tab.
  2. If it is too loose for you, you may loop the straps around the tabs, both bottom and top evenly. (FINE TUNING)

For users who have a smaller face, like children or women, they may wish to shorten the strap to have a tighter fitment for the mask.

To do so :

  1. Lay the strap over the filter lock rings, then loop them onto the tabs, both bottom and top.
  2. If it has reached a somewhat desired length for the user, you can start to adjust it in small amounts by looping the strap around the tabs again, both bottom and top. (FINE TUNING)
  3. If it is still too long for the user, he/she can further shorten it. Unhook the strap from the bottom and top tabs, then criss cross the strap and hook them back onto the tabs, exchanging positions.
  4. After criss crossing the strap, you can start to adjust the length again by looping them around the tabs again. (FINE TUNING)

These are suggestions by us, after going through several tests and sampling, we have decided this is the most suitable method for adjust the length of the straps. Of course, if you found a better way to adjust the straps, feel free to do so! Our straps are highly elastic, they are able to withstand the stress from all the stretching that it has to undergo.

Here is a short video, displaying the adjustment procedure that we have suggested :