Now this is a very specific company. That is why it is called as an RSPM. People design this based on the impactor, here it is a cyclone in this particular instrument. It doesn’t have to be a cyclone, can be anything and it uses a 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. So at the end of it you weigh the filter paper before and after and you get total mass divided by total volume. So you have total volume. So, 1000 liters multiplied by 8 hours into 60 minutes per hour you get total volume in meter cube in liters, total volume is available here. And then whatever is a weight that you collect on the filter paper, you divide by this number you will get concentrations typically, the concentrations of PM in air are reported as micrograms per meter cubed, all standards are recorded in this unit microgram not milligrams per liter micrograms per meter cubed, very small amount.

PM 2.5 is all 24-hour sampling intervals measurement, so, you cannot do anything. So, I cannot get any information on a lower timescale it is all 1-day average, 24-hour average only. But this is ok because it again depends on the objectives. The way we use this data is we are looking at long timescales, we are saying what happens this year, next year in 10 years, what will happen if this industry stops polluting, this industry starts polluting and so on.

What we are looking at in the previous 2 slides is PM 10, PM 2.5 one that is it done, but what if I want a distribution, I want distribution of particle sizes in different sizes how much is there in each size, then I can decide whether. So, this is what is called as cascade impactor, cascade impactor is just an impactor but you have multiple impactors that one place after the other. You can see this schematic diagram here that it is going in the first one, there is the first impact that goes through this one.

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. And, like in investigations is really like, you know, proper investigation or you are looking for clues and you are kind of connecting with what is the cause of these things.

There are other methods of doing real time analysis. I am going to ask a question at the end of this discussion and you have to be prepared for that. There are optical methods in which there is a laser and it is based on scattering principle there is a particle light hits it, it scatters and is based on the scattering law, the amount of scattering and angular scattering depends on the size of the particle.

This is called as an aerodynamic particle sizer. And as the name suggests this exactly does what the aerodynamic diameter definition is. It takes the particle and it finds out what is the momentum of the particle, how fast it is moving at a certain size. And then based on that it calculates, what is the size of the particle? So, there are 2 lasers it calculates how much time it takes for a particle go from one place to another place, and it is a very sophisticated equipment called as APS, this is not an optical method. This is aerodynamic method.