- Emerson Electric Co.
- Teledyne Advanced Pollution Instrumentation
- Siemens AG
- Servomex (Spectris PLC)
- Fuji Electric Co Ltd.
- Honeywell International (RAE Systems)
- Dragerwerk AG
- Otis Instruments Inc.
- Industrial Scientific Corporation
- MSA Safety Incorporated
- Detector Electronics Corporation
- Scott Safety
- Crowncon Detection Instruments Limited
- Microwatt Controls Limited
- Detcon Inc.