U.S. EPA Ground Level Ozone Targets Released

New US EPA Ground Level Ozone Targets Released

             If you’ve ever purchased high-end audio equipment, you’ve probably seen columns of specifications with an endless list of numerical values. With some, bigger is better, with others, smaller numbers have meant improved quality. In addition to total audio bandwidth, one of the most critical values is the Signal to Noise Ratio (SNR). SNR, as its name implies, compares an amplified broadcast signal or recorded source signal tothe background noise that the equipment itself creates. In this case, the larger the SNR, the lower the distortion, and the greater the sound output is to a live performance. SNR’s have always been important in measuring instrumentation output as well. Now, with increasing demands on the detection limits of gas chromatography and mass spectrometry, doing away with response noise has become more critical than ever before. Now we need to look at reducing or eliminating the causes of this noise wherever possible.

In the past weeks, the US EPA released its new ground level ozone target of 70 parts per million (ppm).  Reaching,Obtaining this threshold limit will require a significant boost in atmospheric testing for VOC (volatile organic compounds) in many industrial areas not previously subjected to this monitoring. Depending on the demographic area, air sampling for sixty or more contaminants will be mandated, with special highly accurate multi-component mixtures of these volatile chemicals used to build a baseline. Two different mixtures are available, with the concentrations of these components falling into two ranges, either a high range around 1 ppm, or a lower range mixture of components at 100 parts per billion (ppb).

As you might imagine, carrier gases now become an integral component of any plan to improve SNR. And because these gases aren’t supplied by the instrument provider, they can often be the most critiqued when questions develop. Where once “commodity type” specialty gas grades like “Zero”, “Pre-Purified” or “Ultra High Purity” would have been acceptable for component detection as low as 500 -1000 ppm, Continuous Emissions Monitoring (CEM) now requires something better. And better means certified lower levels of impurities, with analytical certification of their actual concentration, as well as proper cylinder preparation to reduce wall off-gassing, and minimizing atmospheric contamination while under vacuum. Discharging of these gases also requires the proper pressure reduction device, again minimizing contamination of the system through regulated cleaning and assembly, and the correct choice of materials that will not react with the sample stream.

So what to do? Demand carrier gases that minimize distortion, and provide as flat a baseline as is practical for the application. If analytical requirements call for accuracy below 10 parts per million, use the best available carrier gases. Look for secondary purification as part of the packaging process, either by absorption media or cryogenic distillation. Ask about cylinder preparation, as the gas is only as good as the container that holds it. And ask about record keeping, and the accuracy of the reference standards, once again because a low level oxygen impurity report is meaningless if the instrument isn’t suitably calibrated, or the calibration gas has no traceability to a defined standard.

Gases like PurityPlus® Grade 6.0 Helium and Ultra Zero Air, with a full certificate of analysis  can easily meet the demands of an increasingly precise world. Try them, you’ll be well satisfied.

For additional details about Mississippi Welders Supply Co., Inc. and its large selection of specialty gases and specialty gas equipment, we can be contacted at (507) 454-5231 or via email at winona@mwsco.com.
October 14, 2015
Rich Mansmann