1. Introduction

1. Introduction

1.1 Engineering Problem

Transboundary smoke haze from land and forest fires during the traditional dry period between June and October has been a recurrent feature in the southern ASEAN region in the past few decades. These annual fires are caused mainly by land clearing and “slash and burn” agricultural practices in Indonesia, particularly Sumatra and Kalimantan (MSS, 2007). The haze consists of many different pollutants, one of which being carbon monoxide (CO) (NEA, 2014). Worried about their health, people would want the air in their homes to be cleaner. The first solution they would think of would be to wear a disposable mask. However, disposable masks cannot completely protect a person from the harmful chemicals in the air as there may be leakages (Department of Health, 2011). Hence, we are trying to design an air purifier and a carbon monoxide sensor to work side by side for the sensor to prove the devices efficiency and also to keep track of carbon monoxide levels in the air.

1.2 Engineering Goal

We aim to find out how arduino works with an air quality sensor and purifier, as well as how the different systems work differently to remove different harmful chemicals or particles in the air. By researching and learning about arduino and the different systems, the collected data will be used to develop an environmentally friendly and effective air quality sensor and purifier to make sure the air in the house will be clean and healthy for residents, especially asthmatic people or people with allergies, to inhale. Thus, the air in the house will be healthier for people to breathe.

With our device, we aim to decrease the carbon monoxide levels from 2000ppm to less than 20ppm of carbon monoxide in the time span of ½ an hour.

1.3 Specific Requirements

Our engineering requirements that we hope to achieve include the following:
  • Our air purifying device will have to be environmentally friendly
  • Our air purifying device must make sure the air in houses are clean enough to be safe for asthmatic people or people with allergies
  • The carbon monoxide sensor must be connected to the air purifying device, such that if the carbon monoxide levels are too high, the air purifying device will turn on automatically
  • The air purifying device can decrease carbon monoxide levels from 2000 ppm to less than 20 ppm of carbon monoxide in the time span of ½ an hour

1.4 Alternative Solutions
1.41 Water Based Air Purifier

How it works

There is a rotary fan that is attached to the top. When the rotary fan is turned on, it moves the air at a higher speed which decreases the air pressure (Cliff J, 2005) and causes the air to enter the container which is the body of the air purifier. When the air flows through the water, the dirt in the air is collected in the water and then clean air exits the container.

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How it is built

Materials needed :
- CD container
- rotary fan
- screws
- vacuum filter

Model : Having flipped the CD container upside down, the cover of the CD container will be replaced with the rotary fan. The rotary fan will be secured with screws. The screws will be secured with bolts to ensure the rotary fan stays in place. There will be slits cut into the sides of the container above water level to let the clean air escape. Water is in the container to collect the dirt. To ensure that the air leaves the container as clean as possible, there are sheets of vacuum filter dryer sheets covering the slits of the container (Hamed . A, 2009).

1.42 HEPA filter / Adsorbent (Activated carbon air filter - Charcoal (treated)) /UV light air purifier

How it works

HEPA: It works by forcing air through a fine mesh that traps harmful particles such as pollen, pet dander, dust mites and smoke from cigarettes (WebMD, LLC, 2012). Most of the airborne pathogens which measure more than 0.3 micrometers in length will be removed (Becky Metivier, 2012) .


Absorbents: Most of the absorbents sold in the market are also known as activated carbon air filter which is charcoal which has been processed to absorb more chemicals than unprocessed charcoal (HowStuffWorks, 2000). This filter can absorb fumes, odors and chemicals (Michigan State University Extension, 2003). The activated carbon air filter has to be changed from time to time (Aquariacentral, 2008).

UV Lights: Microorganisms and viruses cannot survive being under the UV lights. Hence, these harmful organisms will be removed from the air before they reach the human nose (Ben Davis, 2014).

1.43 Ionic Air filter

How it works

Ionic air filters rely on voltage to charge air molecules. Typically, they produce negatively charged ions, also called anions, which then attract particles in the air, in much the same way as static electricity. As the particles make contact with the anions, they are de-ionized and removed from the air stream. However, this type of air purifier produces ozone which is a potential pollutant and irritant. The devices also don't effectively remove dust, dander and other irritants from a room. Without fans, they can't collect airborne particles from more than a few feet away. And when even small amounts of dust enter the device, the plates inside quickly lose much of their power to attract more particles. Meanwhile, the charged particles that stick to walls or TV screens haven't left the room and can always billow up again to cause trouble (Chris Woolston, 2008).
Materials needed:
- Magnetic Plates
- Ion generator and fan mechanism

1.44 Final Solution

After much evaluation, we decided that our best design is design 1. This is because the materials are easy to find and the idea is very feasible, it is also very effective in removing air pathogens, it also does not produce pollutants like the ionic air filter (Ben Davis, 2014). However, after deeply thinking through the design again, we decided to combine both designs 1 and 2. This is because the combined designs will be much more effective in removing the different pollutants in the air. It is more effective in the sense that more air can be filtered at once, and the more harmful type of pollutants will also be removed.

Due to safety reasons, the section that will be filled with water should be separated from the electrical components in the air purifying device as the water can cause the wires to short circuit. Because of this, our device will be made of two different boxes, one for the air to enter and pass through the HEPA filter and one for the water based air purification. Since there are two different boxes that the air is supposed to travel through to get purified, we have decided to add an air pump in the first box to lead the air into the second box through air tubes. Within the air pump, there are also additional air filters (Wikipedia 2014). This adds onto the efficiency of our air purifying device.

One thing to take note of for the air pump is that the base of the air pump has to be above water level so as to ensure that the water in the second box will not backflow into the air pump and spoil it (Wikipedia, 2014).

The main changes that are going to be taking place is the adding of the HEPA filter and Totobobo masks. We are also going to remove the UV lights and change the arrangement of the entire system. We added extra filters because we found out that the water-based filter alone will not be able to completely filter the air and get rid of all the pollutants from the haze as water will only be able to remove the dust and dirt (Top Purifier Reviews, 2014). The HEPA filter and Totobobo masks will be able to filter pollutants like PM2.5, which is one of the main pollutants during the haze season.

We decided to remove the UV lights because UV lights are used to kill microorganisms and viruses in the air (Gary Zeman, 2014). The main purpose of our air quality sensor and air purifier system is to purify the air by removing dust particles, dirt particles and the harmful pollutants in the air. Hence, killing microorganisms and viruses are irrelevant in the system and are therefore not included in the final design.

The finalised design works by having the polluted air (different amounts of smoke which contains carbon monoxide) enter the air purifier through the rotary fan. The rotary fan speeds up the rate at which air enters the air purifier and also ensures that the polluted air passes through the system quickly. The air will then pass through the Totobobo mask, which is placed right at the opening where air enters the air purifier. The Totobobo masks acts as a pre-filter and having the polluted air pass through the Totobobo mask first will also ease the other filter’s load of purifying the air. This ensures that larger dirt and dust particles are filtered before the air moves on through the air purifier system whereby smaller pollutants in the air will be filtered out.

In design 1, we used vacuum filter dryer sheets. However, after further research, we found out that vacuum filter dryer sheets can only filter out dust and dirt (Wikihow, 2014). We then decided to replace the vacuum filter dryer sheets with Totobobo masks. Totobobo masks are a type of mask that filters the smallest pollutants up to the size of 0.1 µm (AQICN, 2013). This means that this mask is able to filter out the most dominant pollutant PM2.5 which measures 2.5µm, as well as other pollutants. The Totobobo mask is actually an extra precaution in the air purifier system to ensure that most of the pollutants in the air during the haze period, especially PM2.5, is removed. Hence, ensuring good air quality in the “room” (our testing area).

The first filter we decided to add from design 2 is the HEPA filter. After the air passes through the Totobobo mask, the air will then pass through the HEPA filter. We did some research on the HEPA filter and found out that HEPA filters are able to remove air pathogens larger than 0.3 micrometers (Becky Metivier, 2012). The main pollutants in the air during the haze are particulate matter (PM10), fine particulate matter (PM2.5), sulphur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO) (Baker, 2012).
Image showing the size of PM2.5 and PM10

PM10 particles are less than 10µm in diameter and PM2.5 are less than 2.5µm in diameter so the HEPA filter will still be able trap the PM10 and PM2.5 particles, since the HEPA filter can filter particles that have a diameter greater than 0.3 µm.

Sulfur dioxide is a compound made from 1 sulfur atom and 2 oxygen atoms. One sulfur atom is 0.000104 µm in diameter and one oxygen atom is 0.000074 µm in diameter (McClure, 2009). A sulfur dioxide particle is estimated to be about 0.000252 µm in diameter.

Nitrogen dioxide is a compound made from 1 nitrogen atom and 2 oxygen atoms. One nitrogen atom is 0.00015 µm in diameter and one oxygen atom is 0.000074 µm in diameter. A nitrogen dioxide particle is estimated to be about 0.000298 µm in diameter.(Noreen D. Poor ,2000)

Carbon monoxide is a compound made from 1 carbon atom and 1 oxygen atom. One carbon atom is 0.00022 µm in diameter and one oxygen atom is 0.000074 µm in diameter. A carbon monoxide particle is estimated to be about 0.000368 µm in diameter (National Physical Library, 2014).

Since the diameters of sulfur dioxide, nitrogen dioxide and carbon monoxide are lesser than 0.3 µm, none of them will be able to be filtered by the air purifier system. However, this is not a huge problem as the most dominant pollutant during the haze season is PM2.5, and the main priority of the air purifier’s system is to remove the most dominant pollutant.

After passing through the Totobobo masks and HEPA filter, the air will then enter the air pump which will lead the air to the second box. The second box is filled with water that has a water level lower than that of the air pump. This prevents the backflow of water into the air pump (Wikipedia, 2014). The air pump has three main components: the transformer, the magnet and the airbag. When the air pump is turned on, the transformer will have two poles which will cause the magnet to repel and attract, thus causing the magnet to vibrate up and down very quickly and press the airbag that will then pump the air through the tube. Pumps operate by generating pressure differences between intake and outgoing valves (Nick Silcox, 2011). Aeration pumps take advantage of the force air places on water in a tube. As air is pumped into a water tube, the continuous stream of rising bubbles “drags” water along its upward motion (Michael Rosenfield, 2014). This causes a displacement in the water, stirring it and causing any left over dust that has not been filtered out to mix into the water. Aromatics is added to the water so that the air that exits the air purifier system will be nice-smelling. The water-based filter filters the air by removing dirt and dust particles. This means that the water-based filter will have the same function as the Totobobo masks. However, unlike the Totobobo mask, the water-based filter is actually an extra filter which filters dust and dirt particles in case the Totobobo masks and HEPA filter did not manage to filter those particles.

The cleaned air then exits the air purifier system through the opening where the second rotary fan is in place in the second box.

The following is the finalized design for our air purifier system: (This design does not include the air quality sensors and the area where the pollutants will be generated to test our prototype.)

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Our design is also incorporated with a carbon monoxide sensor. The carbon monoxide sensor is placed at the location as shown in the experimental setup picture below at the data analysis section.

After further consideration, we have concluded that making the air purifier turn on and off solely according to the readings of the carbon monoxide sensor is too ambitious. Thus, the development of the carbon monoxide sensor is only for the representation of the air quality in the room to test the efficiency of our device.

Our methods of going about doing this project would be to research on the problems faced by people during the haze season, past air purifier projects and products, the different types of filters, the different types of systems, different types of pollutants and chemicals as well as their sizes on the internet and in the national libraries. Then, using the collected data, we will choose from 3 different designs of air purifiers. The 3 designs are water based air purifier, HEPA air filter and Ionic air filter.

We were going to choose design 1 to build. However, after thinking about design 1 again, we decided that it was not very efficient in removing all the harmful pollutants in the air during the haze period. Hence, we decided to combine designs 1 and 2 to ensure that our air purifier is able to remove all the pollutants in the air. Design 3 was not chosen because ionic air filter releases pollutants into the air, which is the opposite of what we want (pollutes the air instead of purifying it).

The carbon monoxide sensor is mainly made with an MQ-7 sensor, which is sensitive to carbon monoxide (Tracy Allen, 2012), and the Arduino Black. Our reason for using a carbon monoxide sensor is because there is carbon monoxide present in the haze as stated in the section of “Problem being addressed”. Thus, we are using carbon monoxide levels to represent air quality in this experiment.

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