4.1 Key findings
1] The air purifier was successful in decreasing the carbon monoxide level in the testing box from an average of 2008 ppm to 979 ppm in 30 minutes.
2] By looking at our graphs we can see that our air purifier is successful and it is constantly clearing the carbon monoxide in the surrounding air by halving the current values every 25 minutes as explained below. However, it is unable to decrease carbon monoxide levels until they are less than 20 ppm in the time span of 30 minutes.
After analysing the line graph that was made for the average carbon monoxide levels for all experiments against time, we concluded that the line in the line graph will be a curve that would never touch the x-axis as the values can only keep halving themselves after a fixed amount of time. We have also estimated the time taken for the ppm of carbon monoxide to decrease by half to be 25 minutes as shown below.
With the estimation that 25 minutes is needed for the ppm of carbon monoxide at that point of time to decrease by half, we can also estimate that our device will take about 3 hours and 20 minutes to decrease carbon monoxide levels from just over 2000 ppm to a reasonable and safe level of 8 ppm.
3] Sometimes the levels of ppm of carbon monoxide read would fluctuate by about plus or minus 300 ppm.
4.2 Explanation of key findings
1] A few of the main components that played a big part in the success of the air purifier were the HEPA filter and the totobobo masks. Below is a picture showing the outcome of the totobobo mask after the experiment.
The totobobo masks on the left are brown and dirty, thus proving that it is efficient in trapping the dirt particles. The totobobo masks on the right are clean ones to act as a control and for comparison purposes.
2] The air purifier was unable to make carbon monoxide ppm levels less than 20 ppm in the time span of 30 minutes. This is probably due to the fans as they are very weak and this affects the efficiency of the device. Another possibility was because we used an unreasonable amount of smoke. Because of that, 20 ppm, which is a very low value, would be harder to achieve in such a short time since the original value of carbon monoxide was so high.
3] The fluctuation of carbon monoxide readings are probably due to three different possibilities. The first being the MQ7 sensor had not been preheated for 48 hours at least, thus leading to inaccurate results. The second reason being there were a few holes in our setup that we missed out and the carbon monoxide leaked out. The last reason could be because the carbon monoxide did not circulate around the box properly due to the displacement caused by the rotary fans.
4.3 Evaluation of engineering goals
We met our goal of using the collected data of arduino and different filter systems to construct an environmentally friendly air purification system and a carbon monoxide sensor by using minimal materials. The cardboard box that we were unable to use was also reused for the border of the HEPA filter. This filter is environmentally friendly as it does not release harmful chemicals like the ionic air filter. One main component of the device, which is the HEPA filter, does not even make use of any electricity. We also reused some old materials like the metal box for the air pump stand and the old plastic biscuit container for the collection of smoke. After testing our air purifier, concluded that our air purifier system and carbon monoxide system works and our project is a success. However, the air purifier system was ineffective in purifying the air and we did not manage to reach our goal of building an effective air purifier system.
Before building the air purifier system, we researched on the different types of filters and found out how the different systems work differently to remove different harmful chemicals or particles in the air. Therefore, we met our goal of building knowledge of harmful chemicals or particles in the air, as well as how the different systems work.
After building our air purifier system and carbon monoxide sensor system, we had to combine both systems to archive our goal. However, we did not manage to combine the systems and both systems had to be utilized separately and controlled manually.
Throughout the whole development process, we have also learnt a lot more about how the MQ7 carbon monoxide sensor works and we have a deeper understanding for arduino. One of the things we were not able to achieve was getting the ppm of carbon monoxide to be less than 20 ppm in half an hour. We were also unsuccessful in making the air purifying device automatic, where it would have turned on by itself if the carbon monoxide levels were too high, as we had planned to do so at the very beginning of the project.
4.4 Areas for improvement
One of the most important things we can work on is safety. We accidentally caused one of the walls of the container that we were burning the paper in to melt as we did not put out the fire properly. We could also be more careful while soldering the wires to the sensor as too much heat could possible burn out the filament in the sensor and permanently damage the MQ7 carbon monoxide sensor.
The fans in our device are very weak and this results in poor efficiency rates. We should do our research on the voltage of fans next time and be more prepared when picking the fans so that our fans will be more powerful. We can also use more airtight containers for the main compartments of our device so that it will increase the efficiency of our device and ensure that the experiment is fair.
For the MQ7 carbon monoxide sensor, we should have been prepared with a better code that used a more accurate equation such that the readings from the sensor would be more accurate. We could also preheat the sensor for more than 48 hours so that our readings would be more accurate and not fluctuate so much.
The maximum haze level in Singapore was about 400 PSI (BBC News Asia, 2013). If we were to repeat the experiment, we could calculate the ppm of carbon monoxide found in 400 PSI of haze. We can then find a way to produce that much carbon monoxide and test our air purifying device to see if it is able to clear all of that carbon monoxide. With those results, we can then make a more accurate conclusion on whether our device was effective for the haze situation in Singapore.
We will need to further study the way the arduino system works with the carbon monoxide sensor as we were not able to achieve the goal of having the air purifier system turn on automatically when carbon monoxide levels in the air reach a certain level. We could not achieve our goal due to time constraints and lack of information.