3.1. Cascade Impactor Design

So, PM sampler is high volume sampler, you can use measurement you can measure it using a 4 digit balance, but then you are losing information because your sampling period is now 8 hours minimum sampling period of 8 hours in a urban area where you have a reasonable amount of dust. If you go to a very pristine area, you may not get anything in it, you may have to run it for 24 hours to get something.

High volume samplers, like PM samplers, are devices used to measure particulate matter (PM) in the air. They require a sampling period that can be quite long—usually 8 hours in urban areas. However, this extended sampling time can lead to a loss of critical information about air quality, especially if the area is less dusty.

Imagine you’re trying to measure how much rain falls in a city during a storm by collecting water in a bucket. If you only collect water for 8 hours, you might miss the heavier downpour that happens right after you stop collecting, similar to how a long sampling period might overlook short bursts of pollution.

Somebody says I have an instrument which will measure PM10 for 1000 rupees. Everybody will shift to that now, because you can get wide network of these instrumentation and that is it. And if you can prove that it is correct accurate, then that will be the new standard now.

The design of impactors, which are used to capture specific sizes of particulate matter, is critical for accurate measurement. When a more affordable instrument, like a PM10 device for 1000 rupees, becomes available and proves to be accurate, it can set a new standard in measurement technology. This shift can greatly enhance the network of air quality monitoring devices deployed.

Think of this as a new budget smartphone with a great camera. If it gets positive reviews for photo quality, many people will switch to it, leading to its widespread use. Similarly, an affordable and accurate PM measurement tool can change how we monitor air pollution.

Large filter paper which is a sheet that uses a glass microfiber filter of 8 by 10 inches which is like an A4 size sheet, large filter paper. And you can sample 8 hours and 1000 liters per minutes, large volume you can imagine how much of air is going through that so the amount of particulate it collects is significant.

Impactors utilize large filter paper to capture airborne particulate matter. The filter, often made of glass microfiber and measuring 8 by 10 inches, allows for significant air flow—up to 1000 liters per minute over an 8-hour sampling period. This means a considerable volume of air is processed, capturing a significant amount of particulates for analysis.

It's like using a large vacuum cleaner to clean a room quickly. The bigger the vacuum, the more dirt it can gather in a shorter time. Similarly, a larger air sampler with high flow rates can collect more dust and particulates over its sampling time.

At the end of it, you weigh the filter paper before and after and you get total mass divided by total volume.

To determine the concentration of particulate matter in the air, the filter paper is weighed before and after air sampling. The mass of the particulates collected is divided by the total volume of air sampled, resulting in a concentration value often reported in micrograms per cubic meter.

Imagine weighing a sponge before and after soaking it in water. The difference in weight gives you the amount of water absorbed. Similarly, the difference in filter weight reveals how much particulate matter was collected.

Cascade impactor is just an impactor but you have multiple impactors that one place after the other.

A cascade impactor consists of several stages, each designed to capture particulate matter of different sizes. As air passes through, the larger particles are trapped in the earlier stages, while smaller ones continue through to later stages. This allows for an analysis of particle size distribution, which is crucial for understanding the types of pollutants present in the air.

Think of a cascade impactor like a sieve set up to strain pasta. The largest holes catch big chunks of food first, while smaller grains slip through to the next grate. In this case, the different stages of the cascade impactor separate particles by size as air flows through.

This is a problem so when you are a regulatory agency you really like to know real time information; you would like to know what is going on real time so that you can focus your energies on fixing where the problem is which is a biggest source of pollution.

Regulatory agencies require real-time data to effectively monitor air quality and identify pollution sources. Instantly available data allows them to respond quickly to pollution spikes and take necessary actions to mitigate environmental impacts.

It's similar to a weather app that provides current readings on temperature and precipitation. Just as you might need to act quickly if a storm is approaching, agencies need real-time data to address air quality issues promptly.

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