Here is a list of spare parts for the Crowcon Sensitron SMART 3-R Gas Detector:
| Sensor Part Number | Description | Detector |
| K4590ME | METHANE detector, 4-20 mA, 0-100% LFL | S4590ME |
| K4590GP | LPG detector, 4-20 mA, 0-100% LFL | S4590GP |
| K4590PR | PROPANE detector, 4-20 mA, 0-100% LFL | S4590PR |
| K4590BU | BUTANE detector, 4-20 mA, 0-100% LFL | S4590BU |
| K4590VB | PETROL VAPOURS detector, 4-20 mA, 0-100% LFL | S4590VB |
| K4591ME | METHANE detector, 4-20 mA, 0-100% LFL | S4591ME |
| K4592PR | PROPANE detector, 4-20 mA, 0-100% LFL | S4592PR |
| K4592BU | BUTANE detector, 4-20 mA, 0-100% LFL | S4592BU |
| K4592DE | R152a detector, 4-20 mA, 0-100% LFL | S4592DE |
| K4629R454B | R454B detector, 4-20 mA, 0-100% LFL | S4629R454B |
| K4626R32 | R32 DIFLUOROMETHANE detector, 4-20 mA, 0-100% LFL | S4626R32 |
| K4627R1234YF | R1234yf detector, 4-20 mA, 0-100% LFL | S4627R1234YF |
| K4628R1234ZE | R1234ze detector, 4-20 mA, 0-100% LFL | S4628R1234ZE |
| K4593O2 | OXYGEN (O2) detector, 0-25% Vol., 4-20 mA | S4593O2 |
| K4595CO | CARBON MONOXIDE (CO) detector, 0-500 ppm, 4-20 mA | S4595CO |
| K4597AM | AMMONIA (NH3) detector, 0-100 ppm, 4-20 mA | S4597AM |
| K4598AM | AMMONIA (NH3) detector, 0-200 ppm, 4-20 mA | S4598AM |
| K4599AM | AMMONIA (NH3) detector, 0-1000 ppm, 4-20 mA | S4599AM |
| K4634CL | CHLORINE (Cl2) detector, 0-20 ppm, 4-20 mA | S4634CL |
| K4601HS | HYDROGEN SULPHIDE (H2S) detector, 0-50 ppm, 4-20 mA | S4601HS |
| K4630SD | SULPHUR DIOXIDE (SO2) detector, 0-20 ppm, 4-20 mA | S4630SD |
| K4632ND | NITROGEN DIOXIDE (NO2) detector, 0-20 ppm, 4-20 mA | S4632ND |
| K4606CO2 | CARBON DIOXIDE (CO2) detector, 0-2% Vol., 4-20 mA | S4606CO2 |
| K4607CO2 | CARBON DIOXIDE (CO2) detector, 0-5% Vol., 4-20 mA | S4607CO2 |
| K4608CO2 | CARBON DIOXIDE (CO2) detector, 0-30% Vol., 4-20 mA | S4608CO2 |
| K4610CO2 | CARBON DIOXIDE (CO2) detector, 0-5000ppm, 4-20 mA | S4610CO2 |
| K4638R32 | R32 detector, 0-5000 ppm, 4-20 mA | S4638R32 |
| K4639R134A | R134a detector, 0-5000 ppm, 4-20 mA | S4639R134A |
| K4640R404A | R404A detector, 0-5000 ppm, 4-20 mA | S4640R404A |
| K4641R407C | R407C detector, 0-5000 ppm, 4-20 mA | S4641R407C |
| K4642R410A | R410A detector, 0-5000 ppm, 4-20 mA | S4642R410A |
| K4643R1234YF | R1234yf detector, 0-5000 ppm, 4-20 mA | S4643R1234YF |
| K4644R1234ZE | R1234ze detector, 0-5000 ppm, 4-20 mA | S4644R1234ZE |
| K4857R1233ZD | R1233Zd detector, 0-5000 ppm, 4-20 mA | S4857R1233ZD |
| K4611R32 | R32 detector, 0-2000 ppm, 4-20 mA | S4611R32 |
| K4612R134A | R134A detector, 0-2000 ppm, 4-20 mA | S4612R134A |
| K4613SF6 | SF6 detector, 0-2000 ppm, 4-20 mA | S4613SF6 |
| K4614R125 | R125 detector, 0-2000 ppm, 4-20 mA | S4614R125 |
| K4615R1234YF | R1234yf detector, 0-2000 ppm, 4-20 mA | S4615R1234YF |
| K4616R1234ZE | R1234ze detector, 0-2000 ppm, 4-20 mA | S4616R1234ZE |
| K4617R404A | R404A detector, 0-2000 ppm, 4-20 mA | S4617R404A |
| K4618R407A | R407A detector, 0-2000 ppm, 4-20 mA | S4618R407A |
| K4619R407F | R407F detector, 0-2000 ppm, 4-20 mA | S4619R407F |
| K4620R449A | R449A detector, 0-2000 ppm, 4-20 mA | S4620R449A |
| K4621R507A | R507A detector, 0-2000 ppm, 4-20 mA | S4621R507A |
| K4622R410A | R410A detector, 0-2000 ppm, 4-20 mA | S4622R410A |
| K4623R417A | R417A detector, 0-2000 ppm, 4-20 mA | S4623R417A |
| K4624R448 | R448 detector, 0-2000 ppm, 4-20 mA | S4624R448 |