Normally, a room containing an irori will not have a ceiling or a floor above it; or, if there is a floor, it is what is called tsushi (つし) or ama (あま), consisting of lashed-bamboo mats (take no su 竹の簀) that allow smoke to easily pass through. In the minka of the mountainous Iya (祖谷) region of Shikoku and in the mountain houses of Chichibu (秩父) in modern-day Saitama Prefecture, none of the rooms have ceilings, and the underside of the roof thatch is directly exposed to the space below. In these houses, a board structure is hung above the irori to catch sparks before they can rise to the roof. This structure is called hi-buta (火蓋, lit. ‘fire lid’), hi-о̄i (火覆い, lit. ‘fire cover’), or the like.

In snowy or mountainous country, one can see a sturdy framed lattice or ‘grille’ (hi-dana 火棚, lit. ‘fire shelf’) suspended over the irori with stout ropes. This device developed out of the hi-buta; in addition to preventing sparks from floating upwards, it plays a role in one of the main purposes of the irori: drying. Wet clothes and snowshoes (yuki-gutsu 雪沓) hanging from small hooks and drying above the fire were once a common sight in minka; seeds and grains (shushi 種子) and other foodstuffs were preserved by placing them on top of the hi-dani.

A sturdy *hi-dana* in the former О̄ta family (*О̄ta-ke* 太田家) residence, originally built in Gifu Prefecture but now standing in the Nagoya City Higashiyama Botanical Gardens. Note the smoke-permeable lashed-bamboo floor above the *hi-dana*. The *irori* uses both a metal pipe type jizai-kagi and a trivet. Smoke and soot from the fire have made the thick ropes holding the *hi-dana* as hard as steel cables.

Hi-dana is the ‘standard’ name, and the one the device goes by in Niigata and Shizuoka, but it is called ama (あま, possibly from an old word for ‘heaven’ or ‘sky’, or perhaps a variant of ami 網, ‘net’) in Mino, hi-ama (ひあま) or hi-amu (ひあむ) in Toyama, and tsuri-ama (つりあま, ‘hanging ama’) or hi-yama (ひやま) in Gifu, among other names. Where the hi-dana developed into a two-tier structure, the lower shelf was often called the ko-ama (こあま, ‘small ama’).

A two-tier *hi-dana* over the *irori* in a *minka* in Kyо̄to City.

With the addition of the hi-dana, a long adjustable hook (jizai-kagi 自在鉤) hanging down from the roof beam becomes impractical to operate for various reasons, so a short, easy-to-handle variety of jizai-kagi is adopted, hung from a stout main hook (oya-kagi 親鉤, lit. ‘parent hook’) that is attached to the centre of the hi-dana. The oya-kagi is also called sora-kagi (そらかぎ lit. ‘sky hook’, with the sense of ‘hook suspended in mid-air’), o-kagi-san (おかぎさん ‘honorable hook-san’), kagi-tsuru (かぎつる ‘hook hanger’), o-kage (おかげ) ‘honorable hook’), and so on.