Overview
ISO 11105:2020 - Small craft - Ventilation of petrol engine and/or petrol tank compartments - specifies ventilation requirements to prevent accumulation of explosive petrol vapours in small craft (≤ 24 m). It covers both natural ventilation for petrol tank compartments and combined natural + powered ventilation for petrol engine compartments. Personal watercraft are excluded.
Key topics and technical requirements
- Scope & definitions: Applies to permanently installed petrol engines, petrol tanks and portable fuel tank storage on small craft; net compartment volume is used for calculations.
- Compartment separation: Compartments containing petrol engines or tanks must be separated from habitable spaces with continuously sealed boundaries and sealed penetrations.
- Natural ventilation (Clause 5):
- Requires both an intake and an exhaust opening/duct to atmosphere unless the compartment is open to the atmosphere.
- Exhaust openings shall originate in the lower one‑third of the compartment and be above normal bilge water.
- Minimum combined internal cross‑sectional area A is calculated by: A = 3300 · ln(V / 0.14) (A in mm²; V = net compartment volume in m³).
- Intake and exhaust openings should be separated by at least 600 mm where compartment dimensions permit.
- Minimum duct cross‑sections: 1 134 mm² for petrol tank compartments and 3 161 mm² for petrol engine compartments.
- Powered ventilation (Clause 6):
- Each compartment with a permanently installed petrol engine requires an exhaust blower system.
- At least one powered blower per propulsion engine; multiple blowers must operate simultaneously.
- Minimum blower capacity q_r depends on compartment volume V:
- V < 1 m³: q = 1.5 m³/min
- 1 ≤ V ≤ 3 m³: q = 1.5 × V (m³/min)
- V > 3 m³: q = 0.5 × V + 3 (m³/min)
- Blower installation: intake in lower one‑third, self‑draining ducts, separated from natural ventilation ducts by ~600 mm where possible; intake/exhaust separation inside compartment ≥ 380 mm.
- Blowers must have dedicated overcurrent protection; visual power indicator at each blower switch; blower must not be auto‑activated by vapor detector.
- Blower rating test per Annex A: break‑in at 120% nominal voltage for 3 h, test at nominal voltage, correct airflow to standard density 1.2 kg/m³ and produce performance curve.
- Safety & marking:
- Only ignition‑protected equipment (ISO 8846) in petrol compartments.
- Label near the ignition switch: “Operate blower for 4 min before starting engine” (symbols per ISO 11192).
Applications and users
ISO 11105:2020 is essential for:
- Boat designers and naval architects specifying fuel and engine compartment ventilation.
- Boat builders and OEMs installing ventilation ducts, blowers and electrical protection.
- Marine safety inspectors and surveyors assessing compliance.
- Aftermarket installers, service technicians and owners following safe operation and maintenance guidance (owner’s manual requirements).
Related standards
- ISO 8846:1990 - Electrical devices - Protection against ignition of surrounding flammable gases
- ISO 10088:2013 - Permanently installed fuel systems (vent openings location)
- ISO 11192:2005 - Graphical symbols for nautical equipment
- ISO 8666:2016 - Principal data (length of hull)
Keywords: ISO 11105:2020, small craft ventilation, petrol engine compartments, petrol tank compartments, exhaust blower, natural ventilation, marine safety.
