Store coal dry, under cover and in low, well-ventilated piles with fines kept apart from lump, because rain makes it hard to light and smoky, and a large, compact, enclosed pile of fine or low-rank coal can heat itself by slow oxidation until it ignites. Probe the piles regularly for warm spots, smell for tar, and break up any heating pile at once.
Part of Coal Surface Mining
Keeping mined coal usable and safe: weather protection, pile size and ventilation, and spotting spontaneous heating.
Why Stored Coal Heats
Fresh coal slowly absorbs oxygen from the air, and the reaction gives off a little heat. In a small or well-ventilated pile the heat escapes. In a large, tightly packed pile air still reaches the coal, but the heat cannot escape, so the temperature climbs and the reaction speeds up until the coal smoulders. The risk is highest with low-rank coals (lignite, sub-bituminous), with freshly mined coal, with fines and dust, and with wet-and-dry cycling that breaks lumps into crumbs. The parent article gives the practical rules: do not store large quantities of fine coal in an enclosed space, and ventilate to prevent heat build-up.
What You Need
- A roof with open sides, or a ventilated shed. A tarp will do for a small pile.
- A raised, drained floor: gravel or boards, so water does not sit under the coal and runoff does not pool.
- A probe: an iron rod you can push into the pile and feel for warmth.
- Separate bays for lump, medium and fines.
Method
Step 1: Build low piles. Keep each pile low and small enough to check by hand. Do not build a high stack of mixed sizes.
Step 2: Segregate fines. Mixed sizes pack tightly; coarse lumps leave air gaps, and the air gaps carry heat away.
Step 3: Shelter from rain. Wet coal is harder to light and smokier (parent). Rain also washes acid and fines from the pile, so drain it away from wells and streams.
Step 4: Check weekly. Push the rod into the pile and pull it out: it should come out cool. Warmth, a tarry smell, steam above the pile or a patch where snow melts first all mean it is heating.
Step 5: Act on a hot spot. Dig out and spread the hot coal thinly to cool and use it first. Do not pour water into the heart of a deep fire, where it channels away and flashes to steam.
Common Mistakes
- Storing in a closed bunker or cellar. Heat has nowhere to go and carbon monoxide collects.
- Putting fresh coal on top of old. Rotate the stock.
- Piling hot ash or clinker near the coal.
Safety
A heating pile gives off carbon monoxide, and a fire can start with no flame
Stored coal that is smouldering releases carbon monoxide long before flames show. Never enter an enclosed store that smells of tar or smoke without ventilating it first, and keep stock away from timber buildings. See Carbon Monoxide Risks.
What’s Next
- Learn next: Burning Coal Effectively — using the stock
- Combine with: Sorting & Grading — what goes in which bay