AS NZS 3580.2.2:2016 pdf free.Methods for sampling and analysis of ambient air Method 2.2: Preparation of reference test atmospheres- Compressed gas method.
6.2 Certified Reference %Iaterial (CRN’i)
6.2.1 General
The CRM shall not contain any foreign component(s) that would invalidate the reference test atmosphere, e.g. oil in a mixture of methane in air to be used for the calibration of a total hydrocarbon analyser, oxygen contamination in a mixture of nitric oxide in nitrogen.
6.2.2 Low temperature
The gas cylinder could potentially be exposed to low temperatures during storage and transportation. For gas mixtures containing condensable components, (e.g. high molecular weight hydrocarbons), it is important that the cylinder is not stored or transported at temperatures below those recommended by the CRM provider. If the mixture is exposed to temperatures below the stated range, some components may condense and this will change the composition of the mixture. If the mixture has been exposed to temperatures lower than those recommended by the CRM provider, the certificate from the CRM provider may be no longer valid. Homogenizing and checking the mixture before usage may be required.
6.2.3 Elevated temperature
Elevated temperatures may result in decomposition of thermally unstable species. Avoid direct exposure to sunlight as this may also heat the cylinder. Avoid high temperatures (heating) close to the cylinder, e.g. from welding flames, blowlamps, ovens or other intense heat sources. High temperatures will result in higher pressures leading to potentially hazardous situations. Cylinders shall not be heated above 45°C.
6.2.4 Water
Gas cylinders shall be protected from excessive humidity during transport. Transportation by boat may result in the cylinder being sprayed with water; this and/or excessive humidity may cause corrosion of the cylinder valve. The cylinder shall he protected from precipitation to prevent corrosion. If the cylinders are stored outdoors, they should be protected by a roof and the cylinder base should also be protected from water accumulating on the floor by raising it above the ground.
6.2.5 Storage and handling
Cylinders shall be stored in a secure manner to prevent rolling and/or falling. For safety reasons, cylinders containing flammable gases shall be separated from cylinders containing oxidizing components. Mixtures containing condensable components may require rehomogenization if stored for extended periods of time and if exposure to temperatures below the condensation point cannot he excluded. This may he done by equilibrating the cylinders to ambient temperature and rotating them in a horizontal position for an appropriate period of time, which will depend on the matrix gas and the components. Homogenizing and checking the mixture before usage may be required.
6.2.6 Mm im u in press lire
The information attached to the cylinder indicates the pressure below which the gas shall not be used. It has been reported that in some cases gas molecules adsorbed to the cylinder wall desorh when the cylinder pressure drops below a certain pressure, resulting in a higher mole fraction. With the following exception, cylinders shall not be used when the gas pressure falls below 700 kPa, or in accordance with the manufacturer’s specifications. This does not apply in the case of certain hydrocarbon mixtures that contain condensable components. In these cases the minimum pressure shall not be less than 10% of the initial cylinder pressure as manufactured, or in accordance with the manufacturer’s specifications.AS NZS 3580.2.2 pdf download.