| 0 | Data points with NULL values in Debbie Miller's RHR data that have a '0' value in the flag_a, flag_b, flag_c, or flag_d field. | Quality Assurance | FLAG_% | M1 |
| AA | ORGANIC ARTIFACT CORRECTED | Quality Assurance | FLAG_% | M2 |
| AP | Possible Organic Artifact | Quality Assurance | FLAG_% | V5 |
| BI | Incorrect installation of sample cartridge during weekly change | Quality Assurance | FLAG_% | M2 |
| CG | Clogged Filter, generally associated with fire impact. The final flow rate is less than one-half of the initial flow rate. | Quality Assurance | FLAG_% | V6 |
| CL | Clogged Filter, generally associated with fire impact. The final flow rate is less than one-half of the initial flow rate. | Quality Assurance | FLAG_% | M3 |
| DA | Did not analyze | Quality Assurance | FLAG_% | M1 |
| DBNULL | Unknown | Temporary | FLAG_% | V4 |
| DE | Derived value | Quality Assurance | FLAG_% | V2 |
| DF | Unknown | Unknown | FLAG_% | V4 |
| EE | Unknown flag | Temporary | FLAG_% | V4 |
| EP | Equipment Problem | Quality Assurance | FLAG_% | M1 |
| LC | Unknown | Unknown | FLAG_% | V0 |
| LD | Below detection limit - at one point this flag was mapped to 'NM' | Quality Assurance | FLAG_% | V0 |
| LF | The flow is greater than 10% higher or lower than the nominal flow rate. This effects the cut point of the particle but the concentrations are correct. | Quality Assurance | FLAG_% | V6 |
| MM | Unknown | Unknown | FLAG_% | V4 |
| NA | Not Applicable. This is used for missing modules with non-protocol samplers with less than four modules. | Quality Assurance | FLAG_% | M1 |
| NM | NORMAL | Quality Assurance | FLAG_% | V0 |
| NR | Samples that have OP=0 that may actually have a negative OP. | Quality Assurance | FLAG_% | V0 |
| NS | Operator did not install the samples or installed them too late to acquire a valid time. All filters involved. | Quality Assurance | FLAG_% | M1 |
| OL | 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. | Quality Assurance | FLAG_% | M1 |
| PC | Possible contamination | Quality Assurance | flag_ | V5 |
| PO | Power Outage. All filters involved. | Quality Assurance | FLAG_% | M1 |
| QA | QA problem suspected, value held back for further investigation | Quality Assurance | FLAG_% | I1 |
| QC | Valid value despite failing to meet some QC or statistical criteria. | Quality Assurance | FLAG_% | V4 |
| QD | Questionable data | Quality Assurance | FLAG_% | V4 |
| RF | The flow is greater than 20% higher or lower than the nominal flow rate. This affects the cut point of the particle but the concentrations are correct. | Quality Assurance | FLAG_% | V6 |
| SA | Used to indicate some sort of 'Sampling Anomaly', though the exact definition has yet to be satisfactorily defined. | Quality Assurance | FLAG_% | V6 |
| SD | Short Duration Sample; The sample is too short for use in calculating RHR metrics, but it is still a meaningful result that is useful in other contexts. | Quality Assurance | FLAG_% | V6 |
| SE | Unknown | Unknown | FLAG_% | V0 |
| SO | Sent Out | Temporary | FLAG_% | V4 |
| SP | An artifact filter was swapped with a sample filter. | Quality Assurance | FLAG_% | V0 |
| SU | A data value from another monitoring site or a modeled/estimated data value has been substituted for the original missing/invalid value. | Quality Assurance | FLAG_% | VS |
| SW | Suspected filter swap. | Quality Assurance | FLAG_% | V0 |
| TO | Timing Outside normal bounds | Quality Assurance | Flag_% | V6 |
| TU | Non-standard sampling conditions | Quality Assurance | FLAG_% | V6 |
| UN | The concentrations failed the data validation for unknown reasons. | Quality Assurance | FLAG_% | M2 |
| XX | The filter is damaged. | Quality Assurance | FLAG_% | M2 |