Question 9 (a) The layering number for gases underground is presented as follows: LNWhereURDSGLN=3(gSG1SGDR)U=airvelocityintunnel=Methanequantityemittedinm3/s=widthoftheairwayinm=SGofMethaneemitted=layeringnumber Through the understanding of layening numbers explain when will layening most probably occur and where? The following additional information is given for the gas and the environment in which it is found: Determine the minimum velocity and related minimum quantity of air required to ensure that layering will not take place. (b) A new blower of methane is exposed and the concentration is 4% methane. This is higher than the legal limit and as ventilation officer you are to calculate the minimum amount of fresh air needed to dilute the gas to within legal limits (comment on your answer). 17 FORMULA PAGE 15