Last updated 6-17-04
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The Air We Breathe: Particulates in inside air

Lab 2 involves trapping air particulates with a portable air pump. This is Melissa. She is using the air pump to pass room air through a cotton swab, which can trap particles in the air. She pointed out that there's an ashtray on the table. I wondered if I would be able to see evidence of cigarette smoke trapped by the cotton.


In her cotton swab were dark bluish particles that probably came from cigarette smoke.

Below is another dark bluish particle found in her sample. Under high magnification, there seems to a clear liquid-like component of this particle.

Also in the same cotton swab, something that looked liquid-like was present. In one "drop" there was a black particle, probably carbon (soot). At some point, I will try to analyze what this shiny substance is. I have to apologize that my experience in the field of microscopy is limited. I did work at the Phoenix Crime Lab for a number of years and did a lot of microscope work. But it was mostly looking at paint chips, human hair, marijuana leaves, and drug crystals. To identify a broad range of items, it takes a great deal of experience. People who specialize in this are called microscopists.

Another student, Alyssa, sent a sample that had a similar bluish particle. This particle had a skull shape, and there's even one eye staring at you. It may also be from cigarette smoke, but I didn't find the liquid-like drops in this sample like I did in Melissa's sample.

Alyssa's sample also had this flake. I suspect that it a flake of dead skin. I don't know if it is human or animal skin. I believe the granular look of this flake is from the individual skin cells.

Another student, Brock, provided a sample that had this particle in it. It looks organic (from something living), but unsure what it could be.

The three large clumps seem to be similar to the single clump above. However, the top two clumps contained a small black particle and a reddish particle. The black particle could be a smoke particle (soot). The red one seemed to be inorganic, like a piece of clay.


Tonya sent in a air-filter sample that only had these small particles clinging to the fibers of cotton. They could be small dust particles.
Lisa sent in a sample that only had these two particles. The small pineapple shaped one at the bottom had the liquid-like appearance that was in Melissa's sample. But this one was much smaller. The small round particle in the inset looked like it could be pollen.

Another student, Claudia, sent in a sample that had this orange, drop-shape particle. No idea what that could be. I'm going to try to get a microscopist to take a look at these pictures to see if identification is possible.

Claudia's sample also contained these strange particles. The bottom one looks like a bent arm with the fingers giving a devil's horns sign. At first it seemed like a fluke, but elsewhere in the sample was another dark particle that also seemed to have these horns.

This is the set up I used to take pictures. A Sony model F717, five megapixel digital camera is attached to a Carl Zeis trinocular microscope. I used the 10x and 40x objective lens (lens over the sample) with 10x ocular lenses (lens by eye) to give 100x and 400x magnifications. A wired remote control was used to trip the shutter .

The camera did a fairly good job, but it didn't pick up all the subtle details or colors that were visible looking through the lens.

I tried to keep an area that was clear of contamination (called a sterile field in the medical community). I first removed the plastic ziploc bag containing the cotton swab from the envelop that the students sent. Using tweezers, I pulled fibers off of the air sample side of the swab and placed them on a new slide and new slide cover. The other side of the cotton swab was used as a control. It wasn't connected to the air pump tubing.

In summary, I thought I would find more particles in the cotton swabs. The pumps were run for 20 minutes, which may not have been long enough. Plus, it may not have been during a time when activities in the house could be stirring up particles or creating pollution. In the case with Heath sampling shown here, I couldn't find any particles; but Heath had recently installed an expensive home air filtering system to help his 8 year old son, Hunter, reduce his exposure to allergens. By the way, this is Hunter's room and the awards are Hunter's football trophies.

So for Heath and Hunter, knowing how well the filtering system was working was very important. From what the microscope could see, it does a good job in removing particulates.

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Since June 17, 2004