| Target Gas Coverage | Confirm that the product is designed for the gases present in the facility, including toxic, combustible, oxygen-deficient, or oxygen-enriched atmospheres. | Common target gases include oxygen, carbon monoxide, hydrogen sulfide, ammonia, chlorine, hydrogen, methane, and volatile organic compounds. Sensor selection must match the gas and concentration range. | Gas list, sensor compatibility chart, measurement range, cross-sensitivity data, and application references. | Critical |
| Sensor Technology | Evaluate whether the sensing principle is suitable for the operating environment and expected gas hazards. | Electrochemical Commonly used for many toxic gases and oxygen.
Catalytic Bead Used for many combustible gases and requires oxygen for operation.
Infrared Used for selected combustible gases and some carbon dioxide applications.
PID Used for detecting many volatile organic compounds. | Sensor principle, expected service life, environmental limitations, poison-resistance information, and replacement procedure. | Critical |
| Measurement Range | Check whether the measuring range covers normal background levels, alarm thresholds, and credible peak concentrations. | The correct range depends on the gas, sensor type, occupational exposure limits, process conditions, and applicable local regulations. A wider range is not automatically better if it reduces resolution at low concentrations. | Datasheets showing measurement range, resolution, accuracy, repeatability, and temperature compensation. | Critical |
| Alarm Configuration | Verify independent low, high, time-weighted average, short-term exposure, over-range, fault, and oxygen-deficiency alarms where applicable. | Alarm set points must be determined by the risk assessment and applicable regulations. Many systems support visual, audible, relay, digital, and control-system outputs. | Alarm-setting menu, latching and non-latching options, relay logic, event history, and alarm reset procedures. | Critical |
| Response Time | Assess whether the detector can respond quickly enough for the release scenario, ventilation pattern, and emergency response plan. | Response time varies with gas, sensor technology, sampling method, tubing length, flow rate, enclosure, and test conditions. Buyers should compare published T90 or equivalent test data rather than relying on a generic claim. | Response-time test conditions, sampling-system specifications, pump flow rate, tubing limits, and alarm activation data. | Critical |
| Accuracy and Calibration | Review measurement accuracy, calibration method, zero adjustment, span adjustment, bump testing, and calibration gas requirements. | Calibration frequency is application-specific and should follow the product manual, site risk assessment, sensor drift history, and regulatory requirements. Calibration gases must have suitable concentration, certification, and shelf life. | Calibration procedure, recommended test interval, calibration certificates, gas specifications, and records-management capability. | Critical |
| Ingress Protection | Confirm that the enclosure can withstand dust, water, washdown, outdoor exposure, and the cleaning chemicals used at the site. | Under IEC 60529, IP65 indicates dust-tight protection and protection against water jets; IP66 indicates dust-tight protection and protection against powerful water jets. The rating does not by itself confirm chemical resistance or suitability for every hazardous location. | IP test report, enclosure material, operating-temperature range, humidity limits, corrosion-resistance information, and installation instructions. | High |
| Hazardous-Area Certification | For potentially explosive atmospheres, ensure that the complete installed configuration is suitable for the zone, gas group, temperature class, and protection method. | Certification schemes may include ATEX, IECEx, UKEX, or applicable national approvals. The exact marking must match the site classification and installation requirements. | Current certificates, product marking, certificate conditions, approved accessories, cable-entry requirements, and regional conformity documents. | Critical |
| Electrical and System Integration | Check compatibility with the existing safety instrumented system, fire and gas panel, PLC, SCADA, building-management system, or remote monitoring platform. | Common interfaces include 4–20 mA, relay contacts, HART, RS-485, Modbus, Ethernet, and wireless options. Interface availability and hazardous-area suitability vary by model. | Wiring diagrams, communication protocol documents, input/output specifications, cybersecurity information, and integration test records. | High |
| Power Supply and Continuity | Evaluate normal power requirements, backup power, startup behavior, fault indication, and safe operation during power interruption. | Fixed systems commonly use site control-panel power, while portable instruments use rechargeable or replaceable batteries. Required backup duration should be based on the emergency shutdown and evacuation plan. | Power-consumption data, battery-runtime test conditions, low-battery behavior, restart settings, and backup-power recommendations. | High |
| Environmental Performance | Match the detector to ambient temperature, humidity, vibration, altitude, pressure, electromagnetic interference, and exposure to dust or corrosive agents. | Performance limits are product-specific. Sensor accuracy and service life can be affected by temperature, humidity, pressure changes, contaminants, and gas exposure history. | Environmental specification table, test standards, vibration and EMC results, operating-temperature limits, and derating information. | High |
| Maintenance and Lifecycle Cost | Compare sensor replacement, calibration, spare parts, specialist tools, service labor, training, and expected downtime. | Total cost of ownership includes purchase price, installation, commissioning, periodic testing, calibration gas, sensor modules, batteries, software, repairs, and disposal. | Five-year or ten-year maintenance estimate, spare-parts list, sensor replacement instructions, service network coverage, and warranty terms. | High |
| Documentation and Traceability | Require documents that support engineering approval, installation, commissioning, operation, maintenance, and audits. | Important records include datasheets, manuals, certificates, calibration instructions, wiring diagrams, inspection reports, firmware information, and revision-controlled drawings. | Document index, sample inspection and test plan, serial-number traceability, change-notification process, and document language options. | High |
| Quality and Production Controls | Assess manufacturing consistency, final testing, component traceability, software control, and handling of nonconforming products. | An ISO 9001-certified quality management system can provide useful evidence of controlled processes, but certification alone does not prove product suitability for a specific gas or hazardous area. | Quality certificate, factory acceptance test procedure, batch records, calibration traceability, product-change policy, and corrective-action process. | High |
| Global Support and Delivery | Consider regional technical support, spare-parts availability, local service capability, lead time, export documentation, and training. | Delivery capability should be evaluated against project schedule, required quantities, replacement-part demand, import requirements, and the availability of trained service personnel. | Regional support contacts, standard lead times, service-level terms, training agenda, spare-parts stocking plan, and references for comparable installations. | Medium to High |
| Acceptance Testing | Define factory acceptance testing, site acceptance testing, loop checks, alarm simulations, bump tests, communication tests, and emergency-response drills. | Testing should verify the complete detection chain: sensor, transmitter, cable, control system, alarm device, shutdown action, and recorded event. Test frequency should follow the risk assessment and applicable requirements. | FAT and SAT procedures, test forms, pass/fail criteria, alarm matrix, commissioning checklist, and training records. | Critical |
