If you are staying overnight on Crater Camp, your operator should provide hyperbaric chambers as a necessity. Crater Camp is one of the highest camps on Kilimanjaro and it is not possible to descend to a lower elevation if you are suffering from acute mountain sickness (AMS). Moreover, you need to ascend higher before you can descend. This can be potentially fatal if there is no other way to treat AMS.
If you are not staying at Crater Camp then hyperbaric chambers are unnecessary because immediate descent is always preferable. For the majority of climbs, hyperbaric chambers are considered to be a luxury safety feature.
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