Fixed VOC detector for an industrial site: Falco 2 or TVOC 2

Choose Falco 2 when you need pumped sampling, relays and Modbus, many ranges or the TAC version. Choose TVOC 2 for simple vapor monitoring at one point: three ranges in one instrument, diffusion, a 4-20 mA output and sensor replacement without opening the explosion-proof enclosure. Both are photoionization (PID) instruments and measure the sum of volatile organic compounds. Below: how they differ, how to choose for site conditions and what to check at installation.

Comparison

Parameter	Falco 2	TVOC 2
Version	diffusion or pumped	diffusion (pump via adapter)
Ranges	0-10, 0-50, 0-1000, 0-3000 ppm; TAC 0-50 ppm	0-10, 0-100, 0-1000 ppm, selectable in one instrument
Sensitivity	from 0.001 ppm	from 0.01 ppm
Response T90	pumped under 10 s, diffusion under 30 s	under 35 s
Output	4-20 mA, RS485 Modbus, two relays	4-20 mA
Lamp	10.6 eV, 10.0 eV (TAC)	10.6 eV
Explosion protection	ATEX/IECEx II 2G Ex db ib IIC T4 Gb	II 2G Ex ia IIC T4 Gb (zone 1 with barriers), II 3G Ex nA IIC T4 Gc (zone 2)
Ingress protection	IP65	enclosure IP65, sensor IP54
Temperature	pumped -20...+50 °C, diffusion -40...+50 °C	-20...+50 °C
Power	8-40 V DC	5-28 V DC
Weight	pumped 2.9 kg, diffusion 2.5 kg	1.3 kg

Detailed pages: Falco 2, TVOC 2.

How to choose

Go through five questions.

1. Do you need relays and Modbus? If the signal must switch ventilation or a siren directly or be read over RS485, take the Falco 2. If a 4-20 mA loop into the control system is enough, the TVOC 2 will do.
2. Can the sensor be placed at the monitoring point? If the place is hard to reach or dangerous, the pumped Falco 2 draws the sample through a tube up to 20 m.
3. Which zone and what protection method? The TVOC 2 in zone 2 works without intrinsically safe barriers (Ex nA); zone 1 needs barriers (Ex ia). The Falco 2 uses an Ex db ib enclosure.
4. Do you need total aromatics? For TAC there is a Falco with a 10.0 eV lamp. Benzene alone is measured by the Titan 2, see Benzene monitoring at an industrial site.
5. What temperature and humidity? The diffusion Falco 2 works down to -40 °C, the pumped version and TVOC 2 down to -20 °C. The Falco 2 tolerates condensate (Typhoon technology protects the sensor); the TVOC 2 is rated 0-95 % non-condensing.

What to consider at installation

• Location and height. Height and density of placement come from the gas safety system design, taking vapor density and sources into account. We give no universal rule: follow the design and the manufacturer's instructions.
• Lamp maintenance. A PID lamp gets dirty. Diffusion sampling fouls it less than a pump, so the TVOC 2 is cleaned less often. The Falco 2 has a Fence Electrode and contamination protection.
• Sensor. In the TVOC 2 the PID sensor is replaced in seconds, and per the manufacturer's documentation a hot-work permit is not needed.
• Calibration. The TVOC 2 is calibrated via a magnetic switch: zero on a carbon filter, span on 100 ppm isobutylene. The Falco 2 has five magnetic buttons for use without opening the enclosure.
• What a PID does not see. A PID does not show methane and many light gases. If such substances are present on site, add suitable sensors. See Methane leak: what to search with.

Typical applications

• solvent and chemical storage;
• refining and petrochemicals, leak monitoring on process units;
• painting and coating, solvent recovery;
• lithium-ion battery manufacture and storage (Falco 2);
• air quality and process monitoring;
• offshore platforms, wastewater treatment (TVOC 2).

What next

Fixed instruments complement portable ones: a Tiger XT walk-through finds the specific leak, and the monitor watches the zone continuously. For the overall picture and choices for other tasks see Which Ion Science instrument to choose and Gas and VOC leak detection with Ion Science PID detectors.

KEG TRK supplies Ion Science instruments in Kazakhstan and helps select the version for the zone and control system. Price on request.