File updated 6/4/2010
IMPROVE Flag List: 
Flag            Implementation  Measurement     Description
AA              3/1/1988        aerosol         Invalidated due to organic contamination of filter
AP              3/1/1988        aerosol         Retrospectively cleared of organic contamination in suspect filter lot
BI              1/1/2000        aerosol         Incorrect installation of sample cartridge during weekly change
CG              1/1/2000        aerosol         Clogging Filter, generally associated with fire impact.  Flowrate less than 18 L/min for more than 1 hour.  This affects the cut point of the particles but the concentrations are correct.
CL              1/1/2000        aerosol         Clogged Filter, generally associated with fire impact.  Flowrate less than 15 L/min for more than 1 hour.  This affects the cut point of the particles but the concentrations are correct.
DE              3/1/1988        aerosol         Derived value
EP              1/1/2000        aerosol         Equipment Problem
LF              1/1/2000        aerosol         Clogged Filter, generally associated with fire impact.  Flowrate less than 15 L/min for more than 1 hour.  This affects the cut point of the particles but the concentrations are correct.
MU              1/1/2000        aerosol         Missing Undetermined (Valid module flag but NULL obs_value)
NA              1/1/2000        aerosol         Not Applicable.  This is used for missing modules with non-protocol samplers with less than four modules.
NM              3/1/1988        aerosol         Normal
NR              1/1/2000        aerosol         Samples that have OP=0 that may actually have a negative OP.
NS              1/1/2000        aerosol         Operator did not install the samples or installed them too late to acquire a valid time.  All filters involved.
OL              1/1/2000        aerosol         Off Line.  In some cases, this is used when the sampler is inoperable due to hurricane or fire.  For year 2000, this is used for the period after the Version 1 sampler is removed and before the Version 2 samples begins operation.
PO              1/1/2000        aerosol         Power Outage.  All filters involved.
QA              1/1/2000        aerosol         QA problem suspected, value held back for further investigation
QD              3/1/1988        aerosol         Questionable data
RF              1/1/2000        aerosol         The flow is greater than 20% higher or lower than the nominal flow rate.  This affects the cut point of the particles but the concentrations are correct.
SA              1/1/2000        aerosol         A sampling anomaly occurred during sample collection.
SP              1/1/2000        aerosol         An artifact filter was swapped with a sample filter and was corrected.
SW              1/1/2000        aerosol         Suspected filter swap which was corrected.
UN              1/1/2000        aerosol         Invalid mass measurement.  All other analyses are valid.
XX              1/1/2000        aerosol         Sample destroyed during sampling or handling.