ChemDAQ’s own Richard Warburton* recently had a paper published in Infection Control Today, the January 13th, 2012 edition. In this article, Richard points out that many people consider chemicals that are safe for the environment are obviously safe for general use. While this may be true for many compounds such as sugar which is generally benign except to our waistlines, Richard argues that an environmentally toxic chemical is one that is persistent in the environment (think DDT or mercury).
In contrast a chemical which is highly reactive is hazardous because of this reactivity but it is environmentally benign because it reacts so quickly that it disappears quickly. He gives the example of pouring either a solution of a cadmium salt or 30% hydrogen peroxide on to the ground. The hydrogen peroxide will fizz and froth and be gone in a few hours, but the cadmium may still be at detectable levels twenty years later in nearby water wells.
The take-home message is not to say that persistent chemicals cannot be harmful; some definitely are, but rather to illustrate that because a chemical product is labeled ‘green’ or ‘environmentally safe’ it doesn’t mean it is necessarily safe for those exposed to it.
* P. Richard Warburton, PhD, JD, is Chief Technology Officer and General Counsel at ChemDAQ Inc.
Thursday, April 12, 2012
Wednesday, April 11, 2012
ChemDAQ Provides a Free Gas Concentration Converter
Gas concentrations are usually expressed in terms of parts per million, or mg/m3. Being able to convert from one unit to another is important since some regulations, industrial hygienists etc. prefer one format over the other. However, converting from one to other is not as simple as converting temperature from degrees Fahrenheit to degrees centigrade because ppm and mg/m3 are not strictly the same thing, mg/m3 is an actual concentration whereas ppm is a relative concentration.
If all this unit conversion sounds difficult, it need not be. ChemDAQ has produced a free unit conversion spreadsheet tool, available for download from the ChemDAQ website (at the bottom of the page). This tool allows simple conversion from ppm to mg/m3 and back again and even provides the molecular weights for many common gases and vapors found in healthcare. If we have missed any compounds that would be useful, please let us know and we will add them to the list.
A more detailed explanation of the difference between ppm and mg/m3 is provided below for those who are interested.
More Detailed Explanation
A concentration is defined as the amount of something per unit volume, so if the amount of a gas is expressed by its weight in mg, then the amount of gas per cubic meter (mg/m3) is the concentration. For a given gas concentration, the mass of gas per unit volume will be proportional to the molecular weight. Thus 1 liter of air has a mass (weighs) about 1.1 g, but 1 liter of 100% chlorine would weigh about 2.8g. The concentration unit of mg/m3 is the mass of the gas per cubic meter.
A part per million, as the name implies, is a relative concentration. If ethylene oxide - air mixture contains 1 ppm ethylene oxide, then for every million air molecules there is one ethylene oxide molecule. Parts per million are particularly useful when dealing with compressed gases, which may be why we use it in gas detection so much. A 2000 psi compressed gas cylinder of 10 ppm ethylene oxide has a much higher internal concentration in terms of mg/m3 than the test gas coming out of the regulator at 1 psi, but the relative concentration of EtO to air, i.e. 10 ppm is the same.
Therefore the relative amount of gas (in ppm) must be multiplied by the molecular weight, as well as changing the units to calculate the weight. In addition to adjusting the units, to convert from ppm to mg/m3, it is necessary to specify a temperature (usually 25 oC) and a pressure (usually 1 atm.).
If the conversion of gas concentrations from ppm to mg/m3 or vice versa sounds involved, use the ChemDAQ gas concentration conversion tool, . The tool is written as an Excel spreadsheet. Enter the concentration (as ppm or mg/m3) in the appropriate box, enter the molecular weight from the handy table shown on the right hand side and the result will be calculated. The converter uses 1 atmosphere pressure and 25oC as a default, but other values can be entered if needed.
Please let us know if you have any comments about the converter, good or bad. If there are any other gases or vapors you would like to see added to the table or other functionality added to the converter, please leave a comment to let us know.
If all this unit conversion sounds difficult, it need not be. ChemDAQ has produced a free unit conversion spreadsheet tool, available for download from the ChemDAQ website (at the bottom of the page). This tool allows simple conversion from ppm to mg/m3 and back again and even provides the molecular weights for many common gases and vapors found in healthcare. If we have missed any compounds that would be useful, please let us know and we will add them to the list.
A more detailed explanation of the difference between ppm and mg/m3 is provided below for those who are interested.
More Detailed Explanation
A concentration is defined as the amount of something per unit volume, so if the amount of a gas is expressed by its weight in mg, then the amount of gas per cubic meter (mg/m3) is the concentration. For a given gas concentration, the mass of gas per unit volume will be proportional to the molecular weight. Thus 1 liter of air has a mass (weighs) about 1.1 g, but 1 liter of 100% chlorine would weigh about 2.8g. The concentration unit of mg/m3 is the mass of the gas per cubic meter.
A part per million, as the name implies, is a relative concentration. If ethylene oxide - air mixture contains 1 ppm ethylene oxide, then for every million air molecules there is one ethylene oxide molecule. Parts per million are particularly useful when dealing with compressed gases, which may be why we use it in gas detection so much. A 2000 psi compressed gas cylinder of 10 ppm ethylene oxide has a much higher internal concentration in terms of mg/m3 than the test gas coming out of the regulator at 1 psi, but the relative concentration of EtO to air, i.e. 10 ppm is the same.
Therefore the relative amount of gas (in ppm) must be multiplied by the molecular weight, as well as changing the units to calculate the weight. In addition to adjusting the units, to convert from ppm to mg/m3, it is necessary to specify a temperature (usually 25 oC) and a pressure (usually 1 atm.).
If the conversion of gas concentrations from ppm to mg/m3 or vice versa sounds involved, use the ChemDAQ gas concentration conversion tool, . The tool is written as an Excel spreadsheet. Enter the concentration (as ppm or mg/m3) in the appropriate box, enter the molecular weight from the handy table shown on the right hand side and the result will be calculated. The converter uses 1 atmosphere pressure and 25oC as a default, but other values can be entered if needed.
Please let us know if you have any comments about the converter, good or bad. If there are any other gases or vapors you would like to see added to the table or other functionality added to the converter, please leave a comment to let us know.
Tuesday, April 10, 2012
Industry News: CSA Publishes New Standard on Chemical Sterilization
The Canadian Standards Association (CSA) has just published its new standard “Chemical Sterilization of Reusable Medical Devices in health Care Facilities” Z314.23-12, available from either CSA or the American National Standards Institute.
CSA Describe the new Standard as follows
Preface
This is the first edition of CSA Z314.23, Effective chemical sterilization in health care facilities. It is one of a series of CSA Standards dealing with the safe and effective sterilization of medical supplies and equipment. It supersedes CAN/CSA-Z314.2, Effective sterilization in health care facilities by the ethylene oxide process, published in 2009, 2001, 1991, 1984, and 1977.
Scope
1.1
This Standard specifies essential elements in implementing a program for using chemicals to sterilize medical devices in health care facilities. Such chemicals can be vapour, gaseous, or liquid and are delivered in validated concentrations and quantities in defined sterilizers.
The body of this Standard contains requirements that are common to all chemical sterilization processes, whereas requirements specific to a particular chemical sterilization technology are contained in Annexes A to E.
The following chemical sterilants are currently approved for use in sterilizers in Canada and are addressed in this Standard:
(a) gaseous and vapour chemicals:
(i) ethylene oxide;
(ii) hydrogen peroxide;
(iii) ozone; and
(iv) hydrogen peroxide-ozone; and
(b) liquid chemicals: peracetic acid.
Exposure to chemical sterilants can present risks to health care personnel and patients; this Standard includes measures to minimize the risk of such exposure as well as discharge to the environment of sterilizing chemicals and by-products.
Further details are available at CSA's website.
CSA Describe the new Standard as follows
Preface
This is the first edition of CSA Z314.23, Effective chemical sterilization in health care facilities. It is one of a series of CSA Standards dealing with the safe and effective sterilization of medical supplies and equipment. It supersedes CAN/CSA-Z314.2, Effective sterilization in health care facilities by the ethylene oxide process, published in 2009, 2001, 1991, 1984, and 1977.
Scope
1.1
This Standard specifies essential elements in implementing a program for using chemicals to sterilize medical devices in health care facilities. Such chemicals can be vapour, gaseous, or liquid and are delivered in validated concentrations and quantities in defined sterilizers.
The body of this Standard contains requirements that are common to all chemical sterilization processes, whereas requirements specific to a particular chemical sterilization technology are contained in Annexes A to E.
The following chemical sterilants are currently approved for use in sterilizers in Canada and are addressed in this Standard:
(a) gaseous and vapour chemicals:
(i) ethylene oxide;
(ii) hydrogen peroxide;
(iii) ozone; and
(iv) hydrogen peroxide-ozone; and
(b) liquid chemicals: peracetic acid.
Exposure to chemical sterilants can present risks to health care personnel and patients; this Standard includes measures to minimize the risk of such exposure as well as discharge to the environment of sterilizing chemicals and by-products.
Further details are available at CSA's website.
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