Enclosed Space Ventilation, Gas-Freeing, Detector & Rescue Readiness Tool | ShipUniverse
MSC.581(110) Enclosed Space Register • Ventilation Time • Gas-Freeing • Atmosphere Testing • Permit • Rescue • SCBA • SOLAS Drill Readiness

Enclosed Space Ventilation, Gas-Freeing, Detector & Rescue Readiness Tool

Screen whether an enclosed space is ready for entry, how long forced ventilation should theoretically take to restore a representative atmosphere, whether portable and personal gas detection is adequate, and whether the staged rescue team has enough breathing-air and retrieval capacity. The tool deliberately separates calculated gas-freeing from the actual atmosphere readings and permit checks that control entry.

Currency
Currency selector changes display only. No exchange-rate conversion is performed.

Space & Hazard Basis

MSC.581(110) treats an enclosed space as hazardous until positively proved safe. Connected spaces can retain a trapped hazardous atmosphere even after the source space has changed condition.

Simple Space Volume

m.
m.
m.
% after structure, framing, cargo residues and internal obstructions.

Advanced Enclosed Space Register

Use this register to compare multiple spaces and record the ventilation time that should be expected for each. Each row is screened independently using its assigned effective blower flow.

Space Volume m³ Flow m³/h O₂ % LFL % CO₂ ppm Toxic ppm Toxic OEL ppm

Forced Ventilation & Gas-Freeing

m³/h at rated condition.
% of rated blower flow reaching the space.
Accounts for dead zones, framing, poor supply/exhaust placement and incomplete mixing.
% volume.
ppm.
Used only for theoretical ventilation-time math. Actual entry requires acceptable measured readings.
% added to calculated gas-freeing time.

Initial Atmosphere for Gas-Freeing Model

% volume.
% of LFL.
ppm.
ppm.
ppm.
ppm.
ppm. Enter the accepted national / company OEL.
ppm. Enter the accepted national / company OEL.
ppm.
% of OEL. MSC.581(110) recommends less than 50% OEL for pre-entry steady readings.

Actual Pre-Entry Atmosphere Test

Calculated gas-freeing time never authorizes entry. Enter the stable readings actually obtained after the ventilation / stabilization / sampling procedure.

% volume. MSC.581(110) states 20.9%.
% LFL. Pre-entry recommendation: less than 1% LFL where relevant.
ppm. Pre-entry recommendation: below 5,000 ppm.
ppm.
ppm.
ppm.
Percentage points. This is a tool screening tolerance, not an IMO replacement threshold.
minutes. Appendix 2 notes about 10 minutes before pre-entry testing.

Gas Detector & Sampling Readiness

MSC.581(110) recommends at least two sets, taking SOLAS XI-1/7 into account.
Compare with maker / SMS interval below.
days. Enter maker / SMS requirement.
m.
L/min.
mm, used to estimate hose purge delay only.

Permit, Isolation & Entry Controls

hours. MSC.581(110) says the permit should never exceed 8 hours.
MSC.581(110) says single-person entry should not be permitted.
SOLAS III/19.3.6 requires relevant crew to participate at least once every two months.

SCBA & Rescue-Team Endurance

L.
bar.
% of nominal cylinder-air volume used in planning.
L/min per rescuer under work load.
minutes.
minutes.
m.
m/min.
kg.
kg.

Ventilation Upgrade / Delay Economics

m³/h before the same duct / mixing derates.
per day.
per hour.
% of theoretical time savings converted to economic value.
Life-safety limitation: This calculator does not authorize enclosed-space entry and must never be used instead of the ship's SMS, Enclosed Space Register, risk assessment, permit, competent / responsible person, atmosphere testing, cargo-specific guidance, flag-State requirements or rescue plan. The exponential ventilation model assumes idealized dilution corrected by user-entered effectiveness and cannot predict pockets of gas, stratification, adsorption/desorption, continuing gas generation, leaks, cargo residues, fumigants or blocked flow paths. Actual atmosphere readings and the ship's approved procedures control entry.
Regulatory / guidance basis: IMO resolution MSC.581(110), adopted 27 June 2025, Revised recommendations for entering enclosed spaces aboard ships; SOLAS regulation XI-1/7 atmosphere testing instruments; SOLAS regulation III/19.3.6 enclosed-space entry and rescue drills; FSS Code chapter 3 SCBA minimum-air / duration reference. MSC.581(110) recommends steady pre-entry readings of 20.9% O₂, CO₂ below 0.5% by volume (5,000 ppm), less than 1% LFL where flammable gas is a credible hazard, and toxic gases below 50% of the applicable occupational exposure limit. Atmosphere testing should be repeated during occupancy, ventilation maintained while occupied, and permit validity should not exceed eight hours. National, flag-State, cargo-code, terminal and company requirements may be more stringent.
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