There are several methods for collecting Pollen used in the United States and throughout the world. The two most common devices are the Burkhard Spore Trap and the Rotorod sampler. Each device has its benefits and its drawbacks. Although the Burkhard spore trap is more efficient at collecting Fungal spores then the Rotorod sampler it is much more labor intensive and the cost of the device is three to four times that of the Rotorod. Both devices seem to be very comparable in efficiency when collecting pollen samples and because the Rotorod is much simpler to set up and the cost is less, it is the sampler of choice for most organizations providing pollen data in the United States.

The Rotorod sampler is a device with a small motor calibrated to run at 2,400 rpm's. It has a timer mechanism that can be set for various sampling periods depending on the anticipated pollen levels. The most common sampling period is a 10% duty cycle where the unit runs one minute and then turns off for nine minutes. This cycle is run over a 24 hour period. We use a retractable head sampling device which contains two acrylic rods. The leading edge of the rod is greased with silicone grease to trap the pollen on the surface as the rods rotate. The acrylic rods retract into the sampling heads between sampling periods to prevent particulates and other pollen from collecting on the surface which could alter the counts or impact the ability to obtain accurate counts.

The 24 hour sampling period is used for certified samples because it is not subject to the variability that a one time sampling has. It provides a more accurate number for looking at long term trends. The downside is that because it is sampled over a 24 hour period the information that you as an allergy sufferer receives is always 24 to 48 hours out of date. For this reason many facilities collect 24 hour data for their certified counts and then collect a daily sample run for a shorter period of time to give the user very current information on what is happening on a given day.

We collect our daily counts over a 25 minute sampling period in the morning when pollen counts are at their peak. We try to have counts completed and information available on our web sit by 10:00 A.M.

Now that the sampling is complete, the next step is to stain the rod with Calberla's stain. We place the acrylic rods into a rod holder and using a pipet we place the stain drop wise down both sides of the rods. A glass cover slip is placed on top of the rods allowing the stain to flow over the surface of the rods. We then wait 15 to 20 minutes for the stain to be absorbed by the pollen. The stain also helps re-hydrate the pollen which helps with the identification. Once stained the pollen is counted under a microscope and the final counts are adjusted to reflect a total count per cubic meter of air. The most challenging part of the process is the counting and identification of the individual pollen. There are three categories of pollen , Trees, Grasses and Weeds. Within these three categories there are literally hundreds of different pollen grains.