| Electrochemical | Carbon monoxide (CO), nitrogen dioxide (NO₂), ozone (O₃), sulfur dioxide (SO₂) | Often 0–100 ppm for CO; many ambient NO₂ and O₃ sensors cover approximately 0–1 or 0–5 ppm | Commonly around 0.01–0.1 ppm, depending on target gas and model | May be specified as a percentage of reading plus a fixed offset. Cross-sensitivity, temperature, humidity, and sensor aging can affect results. | Lightweight and relatively low power. Suitable for localized gas surveys, but each sensor generally measures a specific gas and needs calibration. |
| Photoionization detector (PID) | Many volatile organic compounds (VOCs), typically reported as isobutylene equivalents | Common handheld-style ranges include 0–2,000 ppm or 0–10,000 ppm | Some instruments resolve down to approximately 0.1 ppm; high-sensitivity models may reach lower levels | Response depends on the compound’s ionization potential and correction factor. Readings are not compound-specific without additional analysis. | Useful for finding VOC hotspots. Lamp cleanliness, humidity, and airflow affect readings; it does not detect every VOC. |
| Non-dispersive infrared (NDIR) | Carbon dioxide (CO₂); specialized configurations can measure other infrared-absorbing gases | Common CO₂ ranges include 0–5,000 ppm or 0–10,000 ppm | Typically a few ppm to tens of ppm, depending on instrument design and measurement conditions | Accuracy is commonly stated in ppm plus a percentage of reading. Pressure, temperature, and calibration affect performance. | Good for CO₂ mapping and generally stable over time. Sensor size, power consumption, and pressure compensation matter on small drones. |
| Metal-oxide semiconductor (MOS) | Broad responses to combustible gases and VOCs; target gases depend on the sensing element | Varies widely; some devices report concentrations over ranges from fractions of a ppm to hundreds or thousands of ppm | Highly model- and gas-dependent; a single universal detection limit is not applicable | Often less selective than electrochemical or optical methods. Humidity, temperature, baseline drift, and interfering gases can influence readings. | Compact and inexpensive, making it useful for screening. Best used to identify relative changes or hotspots rather than to confirm a specific gas concentration. |
| Optical particle counter | Particulate matter by size, commonly PM₁, PM₂.₅, and PM₁₀ | Typically reports mass concentration from near zero to several hundred or more µg/m³ | Often detects particles in an approximate size range starting around 0.3 µm; mass resolution depends on the instrument | Reported mass is usually estimated from particle counts and assumptions about size, density, and shape. Results may differ from reference methods. | Useful for mapping particulate concentrations. Rotor wash, inlet placement, particle composition, and high humidity can distort measurements. |
| Optical absorption or open-path laser sensor | Selected gases such as methane, CO₂, or other gases supported by the wavelength and instrument | Instrument-specific; may report concentration over a defined path length rather than at a single point | Depends on path length, wavelength, and instrument design; specifications may use ppm·m rather than ppm | Accuracy depends on optical alignment, atmospheric conditions, path length, and calibration. Results are not directly equivalent to point-sensor readings. | Can survey gas plumes without placing a sensor directly in them. Typically heavier and more power-intensive than compact point sensors. |