Staying Safe in Bromo and Ijen
Part of the Bromo and Ijen travel guide — see every topic in All Bromo and Ijen Guides.
This is the one Indonesian itinerary where the environmental risks are genuinely serious and specific. Ijen's crater emits gas at concentrations that hospitalise people. Bromo's rim is unfenced in places and its crater has killed visitors. Semeru is one of the most active volcanoes in the country and its eruptions have killed dozens in recent years. Cold at altitude catches out visitors arriving from the coast. All of it is manageable, and none of it should be treated casually.
The gas at Ijen
Sulphur dioxide and hydrogen sulphide at the vents reach dangerous concentrations, and the wind shifts without warning. A proper respirator with acid-gas cartridges is essential — a surgical or dust mask does nothing. Check the filter is not exhausted; hired masks are sometimes past their life. If gas comes over you, move upwind and upslope immediately and do not stop for a photograph. Anyone with asthma or a respiratory condition should not descend into the crater and can see the lake from the rim at dawn instead.
The terrain
Ijen's crater descent is a twenty-to-thirty-minute scramble down several hundred metres of loose rock in the dark with no railing, shared with miners carrying ninety-kilogram loads — stand aside for them, always. Bromo's crater rim is narrow, unfenced in sections and windy, and people have fallen. Semeru's summit slope is deep sand at altitude. In all three cases the guide's instruction is the operative one. Wear proper footwear; sandals on the Ijen descent are a genuinely bad idea.
Volcanic activity
All three mountains are active and monitored, and access closes when alert levels rise. Semeru's December 2021 eruption killed dozens in the valleys below, and its summit has been closed for long periods. Bromo's crater has been closed repeatedly. Ijen closes for gas and seismicity. Closures are announced at short notice and are not negotiable. Check the volcanology agency's current status before booking anything non-refundable, and treat an operator who offers to take you into a closed area as a warning sign about everything else.
Cold, altitude and the rest
Temperatures at the Bromo viewpoints drop below five degrees before dawn and Semeru's camps get frost, after a warm drive up from sea level — bring a fleece, a windproof layer, hat and gloves, and do not rely on hiring them. Altitude affects some people above 2,500 metres and more above 3,000. The waterfalls carry flash-flood risk in the wet season and both main sites close after heavy rain. And two consecutive nights of four hours' sleep is itself a safety factor on mountain terrain.
Staying Safe at a glance
| Ijen gas | Requires an acid-gas respirator — check the filter |
|---|---|
| Crater descent | Loose rock in the dark, no railing — give way to miners |
| Bromo rim | Narrow and unfenced in places |
| Semeru | Dec 2021 eruption killed dozens; summit closes for long periods |
| Cold | Below 5°C at the Bromo viewpoints before dawn |
| Always | Check current volcanic alert levels before booking |