The sketch above is an illustration of what is known as the "flux chamber." This device is attached to a tank of gas (usually purified air) and is used to drawn in the air being sampled. Tubing is run from the air tank to the flux chamber, and then another piece of tubing is run from the flux chamber to a vacuum chamber. Inside the vacuum chamber is a Tedlar bag. The amount of air being pumped into the chamber is regulated with a small, hand-held pump that is hooked up to the vacuum chamber. The air from the tank is pumped in at an equal rate to the air being drawn into the Tedlar bag.
This flux chamber is made for use on dry land or in water (see pictures below).
When it is floated on a water surface, a piece of rubber tubing is slipped on
the bottom to ensure that it floats on the surface. This method is especially
effective in collection of air emissions off of aeration tanks. Personally, I
utilized the flux chamber for the collection of emissions from a landfill in
North Attleboro, Massachusetts. In this case, the rubber base was not
utilized; instead, our goal was to actually press the chamber down into the
earth so as to collect the gasses emitted by the landfill and not those
present in the ambient air.
This photograph shows the chamber in an empty
aeration basin.
In contrast, this photograph illustrates the chamber
afloat on the surface of the basin. It is located on the surface in front of
the person standing on the catwalk.
As mentioned previously, tubing is used to connect the flux chamber to the
vacuum chamber. This vacuum chamber resembles a suitcase; it is made so as not
to collapse under a vacuum. The vacuum chamber is connected to a pump which
regulates the flow of air to the chamber. A picture of these two instruments
can be seen below. 
In the photograph below, the pump and the vacuum chamber can be seen in use.
In this case, the system is being used to sample the air quality in a storage
tank.
Not all sampling is conducted with these tools, however. In many cases, a
Jerome meter is used for preliminary readings. A Jerome meter is a
hand-held instrument that is used to detect hydrogen sulfide. This meter is
extremely sensitive to moisture. It has a detection level of one ppb (part per
billion). Often, sampling locations are based upon detection levels obtained
with the Jerome.
The photograph above shows an
engineer sampling air from a duct with the Jerome meter.
The photograph
below again shows the Jerome in use. At this point, the exhaust air is being
monitored for hydrogen sulfide levels with the Jerome, a temperature reading
with a hand-held thermocouple (the yellow instrument with the orange cord) and
the flow rate with a hand held rotameter (the blue instrument to the right of
the Jerome).
In addition to these items, occasionally Summa canisters are used. These are
employed frequently when inexperienced samplers (such as the general public) are
involved. They are simple to use--merely open the top and "grab" a sample.
Once these samples are collected, they are then shipped out for a laboratory analysis. One major concern regarding these samples is their fast expiration--if the sample is not analyzed within 24 hours, it is usually of no use to the sampler. Therefore, these samples must be treated with care.
In many cases, laboratories run tests according to ASTM method D5504 and TO14.
These tests measure the results of the samples received in comparison to a
sample of the background air. A sample of the background air must be taken so
that the laboratory will have a reference.
I hope that this brief introduction has been helpful. I know that I enjoyed
the work I performed at CDM. Listed below
are a few links that are relevant to the equipment I discussed in this
presentation.
SKC Inc., which specializes in the sale of odor and air quality sampling equipment.
St. Croix Sensory, Inc., a laboratory
specializing in odor evaluations.