| 1 | Deviation from a CFR/Critical Criteria Requirement | Quality Assurance Qualifier | Qualifier% | V4 |
| 1C | A 1-Point QC check exceeds acceptance criteria but there is compelling evidence that the analyzer data is valid. | Null Data Qualifier | Qualifier% | V4 |
| 1V | Data reviewed and validated | Quality Assurance Qualifier | Qualifier | V0 |
| 2 | Operational Deviation | Quality Assurance Qualifier | Qualifier% | V4 |
| 3 | Field Issue | Quality Assurance Qualifier | Qualifier% | V4 |
| 4 | Lab Issue | Quality Assurance Qualifier | Qualifier% | V4 |
| 5 | Outlier | Quality Assurance Qualifier | Qualifier% | V4 |
| 6 | QAPP Issue | Quality Assurance Qualifier | Qualifier% | V4 |
| 7 | Below Lowest Calibration Level | Quality Assurance Qualifier | Qualifier% | V4 |
| 8 | QA/QC Unknown. | Quality Assurance Qualifier | Qualifier% | V4 |
| 9 | Negative value detected - zero reported | Quality Assurance Qualifier | Qualifier% | V4 |
| A | HIGH WINDS | Natural Event | Qualifier% | V0 |
| AA | Sample Pressure out of Limits | Null Data Qualifier | Qualifier% | M1 |
| AB | Technician Unavaliable | Null Data Qualifier | Qualifier% | M1 |
| AC | Construction/Repairs in Area | Null Data Qualifier | Qualifier% | M1 |
| AD | Shelter Storm Damage | Null Data Qualifier | Qualifier% | M1 |
| AE | Shelter Temperature Outside Limits | Null Data Qualifier | Qualifier% | M1 |
| AF | Scheduled but not Collected | Null Data Qualifier | Qualifier% | M1 |
| AG | Sample Time out of Limits | Null Data Qualifier | Qualifier% | M1 |
| AH | Sample Flow Rate out of Limits | Null Data Qualifier | Qualifier% | M1 |
| AI | Insufficient Data (cannot calculate) | Null Data Qualifier | Qualifier% | M1 |
| AJ | Filter Damage | Null Data Qualifier | Qualifier% | M1 |
| AK | Filter Leak | Null Data Qualifier | Qualifier% | M1 |
| AL | Voided by Operator | Null Data Qualifier | Qualifier% | M1 |
| AM | Miscellaneous Void | Null Data Qualifier | Qualifier% | M1 |
| AN | Machine Malfunction | Null Data Qualifier | Qualifier% | M1 |
| AO | Bad Weather | Null Data Qualifier | Qualifier% | M1 |
| AP | Vnadalism | Null Data Qualifier | Qualifier% | M1 |
| AQ | Collection Error | Null Data Qualifier | Qualifier% | M1 |
| AR | Lab Error | Null Data Qualifier | Qualifier% | M1 |
| AS | Poor Quality Assurance Results | Null Data Qualifier | Qualifier% | M1 |
| AT | Calibration | Null Data Qualifier | Qualifier% | M1 |
| AU | Monitoring Waived | Null Data Qualifier | Qualifier% | M1 |
| AV | Power Failure | Null Data Qualifier | Qualifier% | M1 |
| AW | Wildlife Damage | Null Data Qualifier | Qualifier% | M1 |
| AX | Precision Check | Null Data Qualifier | Qualifier% | M1 |
| AY | Q C Control Points (zero/span) | Null Data Qualifier | Qualifier% | M1 |
| AZ | Q C Audit | Null Data Qualifier | Qualifier% | M1 |
| B | Stratospheric Ozone Intrusion. | Informational Only | Qualifier% | VE |
| BA | Maintenance/Routine Repairs | Null Data Qualifier | Qualifier% | M1 |
| BB | Unable to Reach Site | Null Data Qualifier | Qualifier% | M1 |
| BC | Multi-point Calibration | Null Data Qualifier | Qualifier% | M1 |
| BD | Auto Calibration | Null Data Qualifier | Qualifier% | M1 |
| BE | Building/Site Repair | Null Data Qualifier | Qualifier% | M1 |
| BF | Precision/Zero/Span | Null Data Qualifier | Qualifier% | M1 |
| BG | Missing ozone data not likely to exceed level of standard | Null Data Qualifier | Qualifier% | M1 |
| BH | Interference/co-elution/misidentification | Null Data Qualifier | Qualifier% | M1 |
| BI | Lost or damaged in transit | Null Data Qualifier | Qualifier% | M1 |
| BJ | Operator Error | Null Data Qualifier | Qualifier% | M1 |
| BK | Site computer/data logger down | Null Data Qualifier | Qualifier% | M1 |
| BL | QA Audit | Null Data Qualifier | Qualifier% | M1 |
| BM | Accuracy check | Null Data Qualifier | Qualifier% | M1 |
| BN | Sample Value Exceeds Media Limit | Null Data Qualifier | Qualifier5 | M1 |
| BR | Sample Value Below Acceptable Range | Null Data Qualifier | Qualifier% | M1 |
| C | VOLCANIC ERUPTIONS | Natural Event | Qualifier% | V0 |
| CB | Values have been Blank Corrected. | Quality Assurance Qualifier | Qualifier% | V2 |
| CC | Clean Canister Residue | Quality Assurance Qualifier | Qualifier% | V5 |
| CL | Surrogate Recoveries Outside Control Limits. | Quality Assurance Qualifier | Qualifier% | V4 |
| CS | Laboratory Calibration Standard | Null Data Qualifier | Qualifier% | M1 |
| D | SANDBLASTING | Exceptional Event | Qualifier% | V0 |
| DA | Aberrant Data (Corrupt Files, Aberrant Chromatography, Spikes, Shifts) | Null Data Qualifier | Qualifier% | M1 |
| DI | Sample was diluted for analysis. | Quality Assurance Qualifier | Qualifier% | V4 |
| DL |
Detection Limit Analyses | Null Data Qualifier | Qualifier% | M1 |
| DN | DNPH peak less than NATTS TAD requirement, reported value should be considered an estimate. | Quality Assurance Qualifier | Qualifier% | V2 |
| E | FOREST FIRE | Natural Event | Qualifier% | V0 |
| EC | Exceeds Critical Criteria | Null Data Qualifier | Qualifier% | M1 |
| EH | Estimated; Exceeds Upper Range | Quality Assurance Qualifier | Qualifier% | V2 |
| F | STRUCTURAL FIRE | Exceptional Event | Qualifier% | V0 |
| FB | Field Blank Value Above Acceptable Limit | Quality Assurance Qualifier | Qualifier% | V4 |
| FI | Filter Inspection Flag | Null Data Qualifier | Qualifier% | M1 |
| FX | Filter Integrity Issue. | Quality Assurance Qualifier | Qualifier% | V5 |
| G | High Pollen Count. | Informational Only | Qualifier% | VE |
| H | CHEMICAL SPILLS & INDUST. ACCIDENTS | Exceptional Event | Qualifier% | V0 |
| HT | Sample pick-up hold time exceeded; data questionable | Quality Assurance Qualifier | Qualifier% | V6 |
| I | UNUSUAL TRAFFIC CONGESTION | Exceptional Event | Qualifier% | V0 |
| IA | African Dust | Informational Only | Qualifier% | V0 |
| IB | Asian Dust | Informational Only | Qualifier% | V0 |
| IC | Chem. Spills & Indust Accidents | Informational Only | Qualifier% | V0 |
| ID | Cleanup After a Major Disaster | Informational Only | Qualifier% | V0 |
| IE | Demolition | Informational Only | Qualifier% | V0 |
| IF | Fire - Canadian | Informational Only | Qualifier% | V0 |
| IG | Fire - Mexico/Central America | Informational Only | Qualifier% | V0 |
| IH | Fireworks | Informational Only | Qualifier% | V0 |
| II | High Pollen Count | Informational Only | Qualifier% | V0 |
| IJ | High Winds | Informational Only | Qualifier% | V0 |
| IK | Infrequent Large Gatherings | Informational Only | Qualifier% | V0 |
| IL | Other | Informational Only | Qualifier% | V0 |
| IM | Prescribed Fire | Informational Only | Qualifier% | V0 |
| IN | Seismic Activity | Informational Only | Qualifier% | V0 |
| IO | Stratospheric Ozone Intrusion | Informational Only | Qualifier% | V0 |
| IP | Structural Fire | Informational Only | Qualifier% | V0 |
| IQ | Terrorist Act | Informational Only | Qualifier% | V0 |
| IR | Unique Traffic Disruption | Informational Only | Qualifier% | V0 |
| IS | Volcanic Eruptions | Informational Only | Qualifier% | V0 |
| IT | Wildfire-U. S. | Informational Only | Qualifier% | V0 |
| IU | Wildland Fire Use Fire-U. S. | Informational Only | Qualifier% | V0 |
| J | Construction/Demolition | Informational Only | Qualifier% | V0 |
| K | Agricultural Tilling | Informational Only | Qualifier% | V0 |
| L | Highway Construction | Informational Only | Qualifier% | V0 |
| LB | Lab blank value above acceptable limit | Quality Assurance Qualifier | Qualifier% | V4 |
| LJ | Identification Of Analyte Is Acceptable; Reported Value Is An Estimate | Quality Assurance Qualifier | Qualifier% | V2 |
| LK | Analyte Identified; Reported Value May Be Biased High | Quality Assurance Qualifier | Qualifier% | V4 |
| LL | Analyte Identified; Reported Value May Be Biased Low | Quality Assurance Qualifier | Qualifier% | V4 |
| M | REROUTING OF TRAFFIC | Exceptional Event | Qualifier% | V0 |
| MB | Method Blank (Analytical) | Null Data Qualifier | Qualifier% | M1 |
| MC | Module End Cap Missing | Null Data Qualifier | Qualifier% | M1 |
| MD | Value between MDL and IDL | Quality Assurance Qualifier | Qualifier% | V4 |
| MS | Value reported is 1/2 MDL substituted. | Quality Assurance Qualifier | Qualifier% | VS |
| MX | Matrix Effect. | Quality Assurance Qualifier | Qualifier% | V4 |
| N | SANDING/SALTING OF STREETS | Exceptional Event | Qualifier% | V0 |
| ND | No Value Detected | Quality Assurance Qualifier | Qualifier% | M1 |
| NS | Influenced by nearby source | Quality Assurance Qualifier | Qualifier% | V5 |
| O | INFREQUENT LARGE GATHERINGS | Exceptional Event | Qualifier% | V0 |
| P | Roofing Operations | Informational Only | Qualifier% | V0 |
| PQ | Values Between PQL And MDL. | Quality Assurance Qualifier | Qualifier% | V4 |
| Q | PRESCRIBED BURNING | Exceptional Event | Qualifier% | V0 |
| QP | Pressure Sensor Questionable. | Quality Assurance Qualifier | Qualifier% | V6 |
| QT | Temperature Sensor Questionable. | Quality Assurance Qualifier | Qualifier% | V6 |
| QV | Quality Control Multi-point Verification | Null Data Qualifier | Qualifier% | M1 |
| QX | Does not meet QC criteria | Quality Assurance Qualifier | Qualifier% | V4 |
| R | CLEAN UP AFTER A MAJOR DISASTER | Exceptional Event | Qualifier% | V0 |
| RA | African Dust | Natural Event Qualifier | Qualifier% | V0 |
| RB | Asian Dust | Natural Event Qualifier | Qualifier% | V0 |
| RC | Chem. Spills & Indust. Accidents | Exceptional Event Qualifier | Qualifier% | V0 |
| RD | Cleanup After a Major Disaster | Exceptional Event Qualifier | Qualifier% | V0 |
| RE | Demolition | Exceptional Event Qualifier | Qualifier% | V0 |
| RF | Fire - Canadian | Natural Event Qualifier | Qualifier% | V0 |
| RG | Fire - Mexico/Central America | Natural Event Qualifier | Qualifier% | V0 |
| RH | Fireworks | Exceptional Event Qualifier | Qualifier% | V0 |
| RI | High Pollen Count | Natural Event Qualifier | Qualifier% | V0 |
| RJ | High Winds | Natural Event Qualifier | Qualifier% | V0 |
| RK | Infrequent Large Gatherings | Exceptional Event Qualifier | Qualifier% | V0 |
| RL | Other | Exceptional Event Qualifier | Qualifier% | V0 |
| RM | Prescribed Fire | Exceptional Event Qualifier | Qualifier% | V0 |
| RN | Seismic Activity | Natural Event Qualifier | Qualifier% | V0 |
| RO | Stratospheric Ozone Intrusion | Natural Event Qualifier | Qualifier% | V0 |
| RP | Structural Fire | Exceptional Event Qualifier | Qualifier% | V0 |
| RQ | Terrorist Act | Exceptional Event Qualifier | Qualifier% | V0 |
| RR | Unique Traffic Disruption | Exceptional Event Qualifier | Qualifier% | V0 |
| RS | Volcanic Eruptions | Natural Event Qualifier | Qualifier% | V0 |
| RT | Wildfire-U. S. | Natural Event Qualifier | Qualifier% | V0 |
| RU | Wildland Fire Use Fire-U. S. | Natural Event Qualifier | Qualifier% | V0 |
| S | Seismic Activity. | Informational Only | Qualifier% | VE |
| SA | Storm Approaching | Null Data Qualifier | Qualifier% | M1 |
| SC | Sampler Contamination | Null Data Qualifier | Qualifier% | M1 |
| SQ | Values Between SQL and MDL | Quality Assurance Qualifier | Qualifier% | V4 |
| SS | Value substituted from secondary monitor. | Quality Assurance Qualifier | Qualifier% | VS |
| ST | Calibration Verification Standard | Null Data Qualifier | Qualifier% | M1 |
| SV | Sample Volume out of limits. | Null Data Qualifier | Qualifier% | M1 |
| SX | Does Not Meet Siting Criteria | Quality Assurance Qualifier | Qualifier | V4 |
| T | UNKNOWN | | Qualifier% | V0 |
| TB | Trip Blank Value Above Acceptable Limit | Quality Assurance Qualifier | Qualifier% | V4 |
| TC | Component Check & Retention Time Standard | Null Data Qualifier | Qualifier% | M1 |
| TS | Holding Time Or Transport Temperature Is Out Of Specs. | Null Data Qualifier | Qualifier% | M1 |
| TT | Transport Temperaure is Out of Specs. | Quality Assurance Qualifier | Qualifier% | V5 |
| U | SAHARA DUST | Natural Event | Qualifier% | V0 |
| V | Validated Value | Quality Assurance Qualifier | Qualifier% | V0 |
| VB | Value below normal; no reason to invalidate | Quality Assurance Qualifier | Qualifier% | V4 |
| W | Flow Rate Average out of Spec. | Quality Assurance Qualifier | Qualifier% | V4 |
| X | Filter Temperature Difference out of Spec. | Quality Assurance Qualifier | Qualifier% | V4 |
| XX | Experimental Data | Null Data Qualifier | Qualifier% | M1 |
| Y | Elapsed Sample Time out of Spec. | Quality Assurance Qualifier | Qualifier% | V4 |
| Z | Other event. | Informational Only | Qualifier% | VE |