The SF6 concentrations from the whole air bag samplers for
the URBAN study are contained in files named IOPnn.CSV, 
where nn is the 2-digit IOP number.  The files are ASCII
files with comma separated fields.  They contain the 
following columns:

IOP number
location number (1-100)
sampler bag number (1-12)
date of sampling start in format: yyyymmdd
time of sampling start in format: hhmm (MST)
length of sampling period in seconds
latitude of location in degrees (e.g. 40.5= 40 degrees, 30 minutes, 0 seconds)
longitude of location in degrees (negative numbers are for West longitude)
SF6 concentration in pptv
data flag


The data flag takes on the following values:

	1 = good data
	2 = below the method limit of quantitation, so view as an estimate
	3 = view as an estimate because of problems in analysis
	4 = unusable data because of problems in the field (e.g missing
	    sample, improper hookup, bag was flat, shot with gun, etc.)
	5 = unusable because of bad analysis in laboratory

If the data flag is 4 or 5, the concentration is set to -999.0 pptv.