 The first step in collecting accurate respirable dust samples is to examine the sampling equipment. The sampling train in this case consisting of a calibrated pump, a 10-millimeter door-oliver nylon cyclone, tubing, hose, breastplate, and cassette must be thoroughly examined. The hose or tubing should be clear and free of holes. The inside of the nylon cyclone must be clean, dry, and free of scratches. The O-ring, where the grit pot attaches, must be present and in good physical condition. The vortex finder should fit snugly on top of the cyclone body. The O-rings in the barrel connector must be present and in good physical condition. The next step is to remove the cassette from its protective bag. Examine the filter in the cassette housing to make sure the filter is flat and not crimped in the housing. It must be placed correctly on the cyclone for proper sampling. Let's take one apart. The reason for doing this is to demonstrate that the cassette can only be attached to the cyclone in one way. As you can see, there are two openings at opposite ends of the cassette. One of these openings is only for inlet air and the other is only for air moving out of the cassette. It is essential that air from the cyclone only enter the opening designated for air entry. Some manufacturers use an arrow to designate flow direction. These particular filter cassettes have a wagon wheel design on the outlet or backside. Remember, the direction of air is from the work area through the opening in the cyclone and then into the filter cassette. Air exits through the tube that is attached to the pump. Why is orientation so important? Look at the parts. This is the filter. As you can see, it is very thin. It's resting on a backing pad. This pad helps protect the filter from damage and keeps the filter in place. The backing pad is on the outlet side of the cassette, closest to the plastic tube that goes to the pump. The filter PVC material is what was weighed at the laboratory and inserted in the cassette. When the cassette is returned to the laboratory, the filter will be removed and weighed again. The difference in weight relates to the amount of dust collected. So, if the orientation of the cassette within the cyclone is correct, dust will be collected on the filter. If the orientation is reversed, dust will be collected on the backing pad and the sample will be ruined. You have just wasted a bunch of time and money. Someone wore that pump 8 to 12 hours for nothing. The backing pad is not designed to collect dust, nor was it weighed prior to sampling. Always check to be sure that you have inserted the cassette correctly onto the cyclone assembly. Note that the cassette has two plugs or plastic covers. They are inserted into the inlet and outlet openings. They must be removed when connecting the cassette to the cyclone for sampling. They must be reinserted after sampling is completed. The purpose of the plugs is to prevent material from entering the openings when sampling is not in progress. Note that they may be different colors, red and blue, for example. Do not assume that one color means inlet and the other outlet. Always examine the cassette to determine which opening is which. For our purpose, the colors mean nothing. Each cassette has a label with a series of numbers. These numbers identify the specific cassette, and the laboratory has a record of the weight of the specific filter contained within the cassette. We will discuss this further when we talk about sampling. But for now, you will use this number to describe your sampling event. Cassettes are fairly rugged, however they should be handled with some care. The cyclone is similar to a cyclone found on plant dust collectors. Its purpose is to separate particles by size. Large particles drop out into the grit pot, and particles smaller than 10 microns in size are directed to the filter that is located inside of the cassette. It is commonly thought that the particles larger than 10 microns in diameter can be rejected from the body by one means or another, so they don't make it into the deeper part of the lungs. The cyclone sorts dust by size and collects on the filter those particles of the size range that could reach our lungs. The cassette containing the small particles on the filter will be sent to the laboratory. The large particles in the grit pot are discarded. Sampling cyclones are precision-made devices manufactured to very tight specifications. They should be handled with care and kept clean. It is important not to damage the inlet, as this could affect the size distribution of the material deposited on the filter. Flow rate was mentioned earlier, and this is extremely important. Cyclones perform their size selection at a certain flow rate. For this cyclone, the flow rate must be 1.7 liters per minute. If the flow rate is significantly higher than 1.7 liters per minute, particles actually smaller than 10 microns will be rejected to the grit pot, and you will lose particles of respirable size that should have gone to the filter. This is because the higher flow rate or velocity within the cyclone artificially imparts weight to particles, and they move to the grit pot where other larger particles go. Conversely, if the flow rate was significantly lower than 1.7 liters per minute, particles actually larger than 10 microns will be collected on the filter. Flow rate is critical. Another potential problem is the orientation of the cyclone. As you can see, the inlet of the cyclone is quite small, and it must be pointing out and away from the miner being sampled. If the opening is turned into the clothing, the sampling result will not be representative of what the person was breathing. Another ruined sample. Connecting the parts of the sampling train is straightforward. Connect the tube from the pump to the cyclone. Ensure that the tube is long enough so the pump can be attached to the belt and still permit the employee sufficient movement to do his or her work.