Interspiro QS II SCBA Air Time Calculator

Select a model, choose your cylinder, enter pressure and breathing rate — duration is calculated instantly.

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Estimated Air Time
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The Interspiro QS II is the long-established workhorse of Interspiro's range, widely deployed in Scandinavian and European fire services. Available with the unique S-mask that includes an ambient air hatch, and upgradeable to SpiroGuide II for telemetry.

QS II vs Incurve: practical fleet considerations

Many departments operate QS II units as their existing fleet while evaluating the Incurve for new procurement. For air time purposes, the QS II with 6.8L 300 bar carbon cylinder is identical to the Incurve with the same cylinder — physics don't change between models. The Incurve's textile-free harness is the primary operational upgrade for departments focused on contamination reduction. If running mixed fleets, this calculator applies equally to both.

The S-mask ambient air hatch: important operating notes

The Interspiro QS II S-mask includes a small ambient air hatch that can be opened to sample air, communicate briefly, or ventilate the facepiece. When the hatch is open, the facepiece is NOT operating as positive-pressure SCBA — the protection envelope is broken. The air supply is unaffected (cylinder air is not consumed through the hatch), but the wearer is exposed to ambient atmosphere. The hatch is designed for staging areas or contamination-free environments only. Never open the ambient hatch in IDLH atmospheres.

QS II without integrated HUD and PASS: managing with gauges

The standard QS II does not include integrated HUD or PASS. Standalone PASS devices must be worn per EN 137 requirements, and air monitoring relies on the mechanical pressure gauge. For crews transitioning from SpiroGuide II (which has HUD and telemetry) to standard QS II, or when using QS II as training units, the gauge discipline protocols used on the QS II reinforce fundamental air management skills that apply regardless of electronics suite.

FAQ

The S-mask includes an ambient air hatch that can be opened to briefly breathe ambient air or communicate. It must only be used in clean, non-IDLH atmospheres. Opening the hatch in a contaminated environment removes all respiratory protection. For air time purposes, the hatch does not consume cylinder air — the calculation is based on demand-valve operation with the hatch closed.

The Incurve is Interspiro's current flagship and recommended for new procurement. The QS II remains in active service at many departments. Both are EN 137 Type 2 certified. Air time calculation is identical for the same cylinder configuration.

The SpiroGuide II is a separate model that adds an electronic monitoring unit to the QS II platform. Whether an existing QS II can be retrofitted to SpiroGuide II depends on the specific unit configuration — consult Interspiro or your local distributor.

Interspiro SCBA Air Time Calculator – Incurve, QS II & SpiroGuide II

Interspiro is a Swedish manufacturer with a long history in Scandinavian fire services and international markets. Their current lineup spans the Incurve (new flagship with textile-free harness), the QS II (proven workhorse), and the SpiroGuide II (telemetry-equipped version of the QS II). All are EN 137 Type 2 certified for structural firefighting. The air calculation is the same across models — what differs is harness design, electronics, and decontamination capability, not the fundamental cylinder and pressure physics.

Interspiro Incurve: textile-free harness and decontamination

The Interspiro Incurve is designed with a fully textile-free harness — straps, buckles, and load-bearing components are all non-textile materials. The primary benefit is decontamination: textile harnesses can absorb contaminants from smoke, HazMat exposures, and chemical environments, making complete decontamination difficult. The Incurve's harness can be fully washed and verified clean. For departments with high-risk exposure environments, this can reduce long-term contamination risk to personnel. Air time is unaffected by harness design.

QS II vs SpiroGuide II: same air, different information

The Interspiro QS II and SpiroGuide II share identical cylinder and air volume configurations. The SpiroGuide II adds an electronic monitoring unit with HUD and — in networked deployments — telemetry reporting. From an air time perspective, both units provide the same usable air for the same cylinder choice. The SpiroGuide II's added value is situational awareness and air accountability, not additional air supply.

SpiroGuide digital display and air management

The SpiroGuide digital display shows remaining air time as a countdown in minutes (calculated at current breathing rate) rather than just pressure in bar. This 'time remaining' display directly matches what this calculator estimates, but it updates continuously based on real breathing rate rather than a fixed RMV assumption. For training, comparing the SpiroGuide's real-time display to this calculator's preset RMV can help firefighters calibrate their personal RMV awareness.

QS II S-mask: ambient air hatch impact

Some Interspiro QS II configurations include an 'S-mask' with an ambient air hatch, allowing the wearer to briefly open the facepiece to ambient air (for communication, sampling, or short-duration tasks). When the ambient hatch is open, the mask is not operating as a positive-pressure SCBA — this does not affect cylinder air consumption, but it breaks the protection envelope. Air time estimates assume continuous closed-circuit positive-pressure operation.

Interspiro cylinder and twin pack options

The Interspiro Incurve and QS II support single cylinders (6.8L or 9.0L at 300 bar) and a twin 3.4L cylinder pack that provides equivalent volume to the standard 6.8L at 300 bar. The twin pack option splits volume across two smaller cylinders — useful where low profile is needed. Total air volume is the same: 6.8L water volume at 300 bar. This calculator treats them identically in terms of air time.

FAQ

The key distinction is the textile-free harness on the Incurve, enabling complete decontamination. The QS II uses traditional textile straps. The Incurve is newer and positioned as the current flagship. Both use EN 137 Type 2 cylinders at 300 bar — air time calculation is identical if cylinder choice is the same.

No. The SpiroGuide electronics are battery-powered and do not consume compressed air. Cylinder capacity and breathing air supply are unaffected by whether telemetry is fitted.

The SpiroGuide display calculates remaining time dynamically based on your current breathing rate at each moment. This calculator uses a fixed RMV preset. If you're breathing slower than the preset, the SpiroGuide will show more time; if faster, less time. The SpiroGuide's real-time estimate is more accurate for your actual breathing rate.

Spirocom is Interspiro's demand valve system used in the Incurve. It operates in positive-pressure mode, ensuring the facepiece remains at a slight positive pressure relative to ambient air, preventing inward leakage even under exertion. All Interspiro models use positive-pressure regulators for structural firefighting applications.

For Interspiro EN 137 Type 2 units operating at 300 bar, 55 bar is the standard department reserve in most European fire services. Some departments operating 9.0L cylinders in complex high-rise or tunnel environments use higher reserves. Always use your department SOP value.

Notes & Safety

This is an estimate based on the values you enter. Real-world air consumption changes with workload, stress, temperature, mask seal, leaks, and individual physiology. Always follow your SOPs and monitor your pressure gauge continuously.

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