1) Gas Explosion: Coal (especially newly-mined coal) emits an inflammable gas (methane) which, when mixed with air, is liable to explode if in contact with a naked light, such explosion being augmented by a following coal-dust explosion in certain conditions. Consequently, coal should be loaded into holds which have been well-aired and, during the first few days following loading, the cargo surface should be ventilated so as to remove any gas, which is liable to seep into nearby spaces – eg: store-rooms. Extreme care should therefore be used when entering cargo-holds or those nearby enclosed areas.
2) Spontaneous Combustion: Coals – particularly soft, bituminous types from the USA and from Poland – are subject to heat and to spontaneously combust. This possibility will depend on the length of time in the ship (the longer coal is laden, the greater the fire risk); the ventilation provided; weather conditions and ambient temperatures; methods of handling the cargo when it is moved about and loaded; and other factors. Generally, the more coal is handled, the more it is prone to emit gas and to spontaneously combust. Although ventilation may be necessary to reduce the risk of gas explosions, such ventilation may encourage spontaneous combustion by directing air on to the hot surface of the coal. Consequently, ventilation of coal must be very carefully supervised and directed at the surface area only, shipboard ventilation systems leading to the bottom of holds being blanked off to avoid air reaching deep into the cargo. The IMO Code of Safe Practice for Solid Bulk Cargoes recommends that temperatures of coal cargo be taken daily at three places in each hold, both near the bottom, and at the middle of the stow. The danger signal is a temperature reading of between 50 and 55 degrees C (l20/l30°F), which indicates that a potential fire hazard is developing. It is imperative that no portion of coals in storage or under transportation be allowed to exceed 80°C (180°F). Thus before loading is permitted to start, temperature of the cargo must be carefully vetted and ‘hot coal’ rejected if too dangerous to carry.
3) Cargo shifting at sea: Especially when loaded wet, small coals – variously termed coal-breeze, slack, slurry or duff – are liable to shift at sea thereby endangering the safety of the ship concerned, particularly small coastal craft lacking self-trimming facilities. Thus it is vital that no suspect cargo is loaded until appropriate water content tests have been conducted by or on behalf of the ship’s master. IMO lays down suggested procedures in such cases, and cargo which is potentially liable to excess surface movement should be rejected. Even if shipped dry, extreme care must be taken with the stowage of small coal which must be well trimmed and stable before venturing to sea.
4) Corrosion of ship’s holds: Coals with a high sulphur content (particularly certain types from the USA) especially when loaded wet, are liable to create a situation whereby chemical action can corrode steel hold sides and bulkheads. This situation may be worsened if the coal temperature rises and, obviously the longer the cargo remains in the ship. Pond coal- coal retrieved from fresh-water ponds – is especially liable to corrode. These problems are further compounded by the practice (commonplace in certain areas of the USA) of loading coals from a variety of sources, each with its own carriage difficulties and requirements.