Bieler+Lang ExDetector SC 220 — semiconductor flammable gas detector

A flammable gas detector with a semiconductor sensor — a very robust one. This is the answer where a pellistor gets poisoned: where the atmosphere contains silicones, hydrogen sulphide or lead compounds. 0–50 % LEL, zone 2.

When a pellistor is not enough

A pellistor measures the heat of combustion on a catalytic bead. That catalyst is vulnerable: silicones (sealants, greases, cosmetics, release agents), hydrogen sulphide and lead compounds deposit on it and permanently reduce its sensitivity. The detector then reads lower than reality — and nobody notices until the next calibration.

A semiconductor sensor works differently: it measures the change in conductivity of a metal oxide layer. Catalyst poisons do not harm it. The manufacturer describes the SC 220 explicitly as a sensible alternative where other sensors cannot be used.

Three sensor versions

The SC 220 is specified for the gas — the sensor comes in three variants: M for methane and hydrogen, P for propane and heptane, S1 for refrigerants including R134a. The version has to be stated when ordering; we will help with the choice.

It works alone or in a system

The detector has integrated low-voltage outputs for pre-alarm, main alarm and sensor fault — so it can trigger protective measures without a controller. In parallel there is a 4–20 mA signal for connecting it to a GMC 8022 or GMC 8034.

The 0–50 % LEL range is narrower than a pellistor’s — and that is fine. Alarms in detection systems are normally set at 10 % and 20 % LEL anyway; the upper half of the scale is territory where nobody should still be in the room.

Technical data

Parameter	Value
Measuring principle	semiconductor gas sensor
Measuring range	0–50 % LEL
Sensor type M	methane, hydrogen
Sensor type P	propane, heptane
Sensor type S1	refrigerants, incl. R134a
Zone	zone 2
ATEX marking	II 3 (2) G · Ex nA de [ib] IIC T4 Gc · PTB 07 ATEX 1002
Stand-alone mode	yes — integrated low-voltage outputs: pre-alarm, main alarm, sensor fault
Measuring signal	linear 4–20 mA
One-man calibration	yes — with the Calibrationbox-i unit
Manufactured in	Germany

Service with us

We are an authorised Bieler+Lang trade and service partner — we hold the manufacturer's written authorisation covering commissioning, maintenance and other service work, valid until 31 December 2028. Our technicians were trained in Achern and work with original parts and factory procedures.

In practice that means we commission, calibrate and service what we sell — nothing has to be shipped back to Germany. See our service scope or send equipment in.