Understanding Parts Per Million (PPM)
Just how much is 50 ppm? That is one of the problems; you are given some exposure limits that you are told these are assumed safe levels, with no real way knowing what level you are being exposed to. It is beyond the scope of this section to address the means how to calculate mathematically approximate exposure levels or how an Industrial Hygienist153 would test for the actual exposure level. So lets look at it from a different perspective:
I would imagine that all of this studying for the A+ test has make you a bit thirsty and perhaps in the need of a little snack. So now you head off to the corner convenience store for a soda and bag of chips. It is your lucky day as this store is having a special: for a small additional price, they will super-size your soda and chips; when they say super size, they mean super size. Your soda will be delivered in a 10,000-Gal (37854.12 Liters) rail tank car, and the chips, all ten tons (9071.85 Kilograms) of them of by tractor-trailer. After your purchase arrives, you realize that maybe it was not such a great deal after all. The soda is warm and the chips need salt. Therefore, you have to add your own ice and salt. In order for the ice not to exceed 50 ppm when added to soda, you would only be able to add approximately 115 one-cubic inch (2.54 cubic centimeters) ice cubes. Then, to do not exceed 50 ppb, you could add no more then 50 pinches of salt to the ten tons of chips. That would be less then one of small packets of salt the fast food places gives out!
Additionally, are the terms Simple Asphyxiantand Trade Secret. Simple Asphyxiant indicates that substance may dilute or displace atmospheric oxygen to an unsafe level. Trade Secretmeans that the manufacturer/importer has withheld the chemical identity because disclosure would cause the loss of an economic advantage that they have over competitors. When the trade secretclause is used, HazCom requires the disclosure of any inherit hazards of these withheld constituents in the MSDS and full disclosure to medical personnel in an emergency. While the standard sets a strict criteria of what may be declared a Trade Secret, there has been much criticism concerning the means of enforcement to prevent abuse. Because this constituent identity has been withheld, an independent evaluation cannot easily be made. Therefore, in many ways, what it comes down is we must trust that the manufacturer/importer (and in this example, it is Tcat) is not pulling a fast one on us.
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