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Overview
Not all calibration gas mixtures are the same — and not all four-gas detectors are calibrated to the same concentration standards. Certain industries, instrument models, and operating environments require a span gas formulation that reflects the specific gas hazards and sensor specifications of their application. The 4-MIX span gas cylinder — CO 50ppm, H2S 25ppm, Iso-Butane (iC4H10) 0.9% / 50% LEL, O2 12%, Balance Nitrogen is one such formulation: a specific four-gas calibration mixture designed for instruments and applications where standard Methane or Pentane LEL calibration is not the correct reference, and where the oxygen sensor needs to be verified against a significantly depleted atmosphere rather than a mildly low one.
Available in cylinder sizes from 34 litres to 116 litres, this mixture is used to bump test and calibrate four-gas monitors across industries where Iso-Butane is the preferred combustible gas reference — including operations involving LPG, natural gas distribution, petrochemical processes, and confined space entry programmes where the detector manufacturer specifies iC4H10 as the calibration gas. The O2 concentration of 12% vol — well below the oxygen-deficient atmosphere threshold of 19.5% — makes this mixture particularly suited to verifying oxygen sensor alarm response in severely depleted atmospheres, which is relevant to enclosed space entry in marine, offshore, and industrial settings.
What differentiates this cylinder from general-purpose four-gas span gas is the combination of Iso-Butane at 50% LEL and oxygen at 12% vol. These concentrations are specified by certain detector manufacturers — including MSA, Industrial Scientific, and others — for instrument models where iC4H10 is the factory calibration gas, and where a lower oxygen calibration point is required to verify the full sensor alarm range. For procurement teams and safety managers sourcing the correct span gas for these instruments, using the right mixture is not optional — the wrong calibration gas will produce a calibration result that does not reflect actual sensor performance against the gases it will encounter in the field.
Key Features
Iso-Butane (iC4H10) at 0.9% / 50% LEL — Manufacturer-Specified LEL Reference for Certain Detectors
Iso-Butane is the preferred calibration gas for the catalytic bead LEL sensor in a number of widely used portable four-gas detectors, including certain MSA instrument models that are factory-calibrated to iC4H10. At 0.9% by volume — equivalent to 50% of the lower explosive limit for Iso-Butane — this concentration provides a mid-range calibration point that confirms sensor linearity and alarm response across the operational detection range. For operations involving LPG handling, butane storage, and gas distribution environments, Iso-Butane calibration also provides a direct gas-specific reference rather than a surrogate calibration gas, which more accurately represents the actual hazard environment.
CO at 50ppm — Higher Calibration Concentration for Elevated CO Risk Environments
Carbon monoxide at 50ppm — rather than the more common 100ppm calibration point — is specified for certain instrument models and used in applications where the detector’s CO alarm threshold is set at or near 35ppm TWA / 200ppm STEL (the OSHA and NIOSH standard limits). Calibrating at 50ppm provides a mid-range verification point that sits above the TWA alarm threshold, confirming that the sensor responds correctly in the range immediately above where the first alarm should trigger. For enclosed spaces with combustion equipment, vehicle exhaust exposure risk, or CO-generating industrial processes, accurate low-range CO sensor calibration is the more critical verification than a high-concentration calibration point.
H2S at 25ppm — Standard Hydrogen Sulphide Calibration Reference
Hydrogen sulphide at 25ppm is the industry-standard calibration concentration for H2S sensors in portable four-gas monitors, placing the calibration point above the OSHA ceiling limit of 20ppm and confirming sensor response in the immediately hazardous concentration range. H2S is one of the most acutely dangerous gases in confined space, oil and gas, marine, and wastewater environments — and an H2S sensor that has not been recently bump tested against a certified calibration gas cannot be relied upon to alarm at the correct concentration in the field. The 25ppm calibration point verifies that the sensor has not drifted below its alarm threshold response level.
O2 at 12% Vol — Severely Depleted Oxygen Atmosphere Verification
The oxygen concentration in this mixture — 12% vol — is significantly below the 19.5% OSHA oxygen-deficient atmosphere threshold, and well below the 16% level at which cognitive impairment begins in most workers. Calibrating the O2 sensor at 12% verifies that the sensor responds correctly to severely depleted oxygen atmospheres, not just mildly low ones. This is particularly relevant for enclosed space entry on vessels and offshore installations, where rapid oxygen displacement by inert gases or product vapours can drive atmospheric O2 levels into the 10–15% range. A sensor calibrated only at 19% may not have its alarm response verified across the full low-oxygen detection range that these environments demand.
Balance Nitrogen — Inert, Stable Carrier Gas
Nitrogen is used as the balance gas because it is chemically inert and does not react with any of the four active gas components in the mixture. This ensures concentration stability throughout the cylinder’s shelf life and prevents cross-interference between gas components during calibration. Nitrogen balance also means the cylinder contents are non-flammable at supply concentrations, making storage and handling straightforward under standard compressed gas cylinder safety procedures.
Multiple Cylinder Sizes — 34L to 116L
The cylinder is available in five sizes: 34L, 58L, 103L, 110L, and 116 litres, allowing procurement teams to match cylinder capacity to the size of their detector fleet and the frequency of their bump testing and calibration programme. Smaller 34L cylinders suit field teams or vessels with a limited number of detectors. Larger 103L–116L cylinders reduce cost per calibration event and minimise cylinder replacement frequency for high-volume calibration operations running daily bump tests across a large instrument fleet.
Technical Specifications
Product Type: Four-Gas Certified Calibration Span Gas Mixture
Cylinder Sizes (C10): 34L / 58L / 103L / 110L / 116 Litres
Carbon Monoxide (CO): 50 ppm
Hydrogen Sulphide (H2S): 25 ppm
Iso-Butane (iC4H10): 0.9% Vol / 50% LEL
Oxygen (O2): 12% Vol
Balance Gas: Nitrogen (N2)
Benefits
Correct calibration gas for iC4H10-specified detector models. Using the wrong calibration gas — even a gas in the same combustible category — produces a calibration result that does not match the sensor’s factory calibration reference, which can mean an over- or under-reading LEL sensor in the field. For instruments where Iso-Butane is the manufacturer-specified calibration gas, this mixture provides the correct reference and eliminates the calibration error that comes from substituting Methane or Pentane span gas.
Full four-sensor verification in a single calibration event. CO, H2S, LEL, and O2 sensors are all verified simultaneously with a single cylinder connection, reducing the time and procedural complexity of calibration against four separate single-gas references. For operations where detector availability is time-critical — pre-entry checks before confined space work, offshore shift handovers, or vessel departure safety checks — a single-cylinder four-gas calibration minimises the time a detector is out of service for calibration.
O2 calibration at 12% provides a more demanding sensor verification than standard mixtures. Most general-purpose four-gas span gas cylinders include O2 at 18–19% — just below the oxygen-deficient threshold — which verifies sensor response at the alarm trigger point. Calibrating at 12% vol verifies the sensor’s response across a much wider low-oxygen range, providing greater confidence that the sensor will alarm correctly even in severely oxygen-depleted atmospheres. For operations involving inert gas systems, nitrogen blanketing, or cargo tank entry on tankers, this is a meaningful difference in calibration thoroughness.
Documented calibration with certified gas supports audit and compliance requirements. Calibration records referencing a certified span gas cylinder — with the mixture specification, cylinder lot number, and certificate of analysis — provide the documentary evidence required for ISM Code safety management system records, OSHA confined space programme documentation, and oil and gas operator permit-to-work audit requirements. A calibration performed with an uncertified or incorrectly specified gas mixture cannot be documented as compliant with these standards.
Flexible cylinder sizing controls calibration cost across different operational scales. Matching cylinder size to detector fleet and calibration frequency avoids both running out of gas mid-programme and paying for significantly more gas than is needed. The five available sizes give procurement teams a practical range of options for managing calibration gas inventory cost and replenishment cycles.
Who It’s For
The Safety Manager Running an iC4H10-Calibrated Detector Fleet
Your site operates MSA or other portable four-gas monitors that were factory-calibrated to Iso-Butane. You’ve been using the correct span gas for field calibrations, but you’re sourcing a new supplier and need to confirm the right mixture specification before placing your next order. You need CO 50ppm, H2S 25ppm, iC4H10 50% LEL, O2 12% — this cylinder is that mixture, available in the cylinder size that matches your detector count and bump testing frequency.
The Marine Safety Officer or Chief Officer on a Gas Carrier or Chemical Tanker
Your vessel operates in cargo environments where oxygen displacement by inert gas or cargo vapour can drive atmospheric oxygen levels well below 19%. Before any tank entry or enclosed space work, you need your four-gas monitor bump tested and confirmed functional — and you need the O2 sensor verified against a low-oxygen atmosphere that reflects the actual conditions in those spaces. The 12% O2 calibration point in this mixture provides that verification in a way that a standard 18–19% O2 span gas cannot.
The HSE Officer at an LPG Terminal or Gas Distribution Facility
Your site handles LPG — which is predominantly butane or propane — and the combustible gas hazard your detectors need to identify is Iso-Butane or a close analogue. Using an iC4H10-calibrated LEL sensor provides a more direct calibration reference for the actual gas your detectors will encounter in a leak or release scenario. This span gas cylinder is the correct calibration reference for your LEL sensors, and the complete four-gas mixture means you can verify all four sensors in a single calibration session.
Possible Applications
- LPG terminals, storage facilities, and distribution operations — Calibration of LEL sensors on portable gas monitors used in environments where butane and propane are the primary combustible gas hazard
- Marine cargo tank and enclosed space entry on gas carriers and chemical tankers — Bump testing of four-gas monitors before entry into cargo tanks, void spaces, and pump rooms where inert gas systems may create severely oxygen-depleted atmospheres
- Offshore platform confined space and hot work programmes — Pre-entry calibration verification for portable gas monitors used in enclosed spaces on drilling and production platforms
- Petrochemical plant and refinery confined space entry — Calibration of iC4H10-specified detector models used by permit-to-work teams entering process vessels, reactors, and storage tanks
- Gas distribution network maintenance and leak detection — Bump testing and calibration of portable detectors used by technicians working on natural gas and LPG distribution infrastructure
- Industrial confined space entry programmes — Calibration of four-gas monitors for workers entering sewers, utility vaults, storage tanks, and enclosed process equipment across manufacturing and utilities industries
- Tunnel construction and underground infrastructure work — Detector calibration for enclosed environments where CO from diesel equipment, ground gases, and oxygen displacement are simultaneous hazards
- Emergency response and HAZMAT teams — Calibration gas supply for four-gas instruments operated by industrial emergency response teams in high-hazard industrial facilities
Trust and Certifications
Certified Calibration Gas Mixture with Certificate of Analysis
Span gas cylinders used for instrument calibration should be supplied with a certificate of analysis (CoA) confirming the actual concentration of each component, the mixture preparation date, the cylinder lot number, and the certified shelf life. The CoA provides the traceability required to confirm that the calibration was performed with a gas mixture that meets the concentration specification — which is the foundation of a valid, audit-ready calibration record. For operations where calibration documentation is reviewed during OSHA inspections, class surveys, or oil and gas operator audits, a certified gas mixture is the correct standard.
Concentration Alignment with Detector Manufacturer Calibration Specifications
The concentrations in this mixture — CO 50ppm, H2S 25ppm, iC4H10 0.9% / 50% LEL, O2 12% — are specified by certain portable multi-gas detector manufacturers, including MSA, for instrument models factory-calibrated to Iso-Butane. Using the manufacturer-specified calibration gas mixture ensures that calibration results are valid under the instrument’s design specification, supports warranty compliance where calibration records are required, and ensures the detector’s sensor response has been verified against the correct chemical reference.
Supplied by Alright Engineering Solutions
This span gas cylinder is supplied by Alright Engineering Solutions Pte. Ltd., a Singapore-based distributor of portable and fixed gas detection equipment, calibration gas mixtures, regulators, and industrial safety instruments. Alright Engineering Solutions serves the marine, oil and gas, petrochemical, and industrial safety sectors across Singapore and the wider regional market, providing span gas supply, instrument sales, calibration accessories, and technical support for gas detection and confined space entry programmes.
Accessories and Variants
Demand-Flow Regulator
A demand-flow regulator connects the span gas cylinder to the detector’s calibration inlet and delivers gas only when the instrument’s pump is actively drawing, preventing gas waste and ensuring accurate sensor exposure during bump testing and calibration. Contact our team to confirm the correct regulator specification for your cylinder valve type and instrument model.
Fixed-Flow Regulator
Fixed-flow regulators deliver calibration gas at a constant specified flow rate and are required for certain detector models that need a fixed gas flow input during calibration. Available in multiple flow rate options to match different instrument calibration inlet specifications.
Calibration Tubing and Instrument Adapters
Silicone or PTFE calibration tubing and instrument-specific calibration cup adapters ensure a leak-free connection between the regulator output and the detector’s sensor inlet. Using the correct tubing and adapter prevents calibration gas dilution with ambient air before it reaches the sensor, which would result in an inaccurate calibration reading.
Available Cylinder Size Variants
34 Litre (C10) — Compact cylinder for small teams, vessel use, or low-frequency calibration requirements
58 Litre (C10) — Mid-range option balancing portability and calibration capacity
103 Litre (C10) — Higher capacity for medium-sized detector fleets with regular bump testing programmes
110 Litre (C10) — Extended capacity cylinder for high-frequency daily calibration operations
116 Litre (C10) — Largest available size for high-volume calibration programmes and fleet-scale daily bump testing
Get in Touch
If you need to source the 4-MIX span gas cylinder — CO 50ppm, H2S 25ppm, iC4H10 0.9% / 50% LEL, O2 12%, Balance N2 — for your gas detection calibration programme, contact Alright Engineering Solutions to confirm cylinder size availability and request a formal quote.
Our team can also advise on compatible regulators, calibration accessories, and portable gas detection instruments to match your specific detector fleet and calibration requirements.
📍 3791 Jalan Bukit Merah #06-01, E-Centre @ Redhill, Singapore 159471
