Before hay steamers were invented a traditional method of removing dust and spores from hay is to soak haynets in a bath of cold water, then leave them to drain.
However soaking hay can wash away essential nutrients needed by a horse - and the water that is left after soaking is considered to be effluent waste in many countries. In addition bacteria and fungal spores are not always destroyed by soaking.
Using a hay steamer to steam hay instead of soaking it can have many benefits as nutrients are retained in the hay and ,as the hay is steamed at high temperatures, (approximately 100 degrees centigrade) most dust mites, bacteria and fungal spores are killed off whilst potentially damaging dust particles are dampened down.
Most hay steamers take 30 - 40 minutes to thoroughly steam hay.
Hay that has been pulled apart or shaken out will take less time to steam that hay which is still compressed in wedges.
You can feed hay as soon as it has been thoroughly steamed.
The hay cools very quickly on the outside - which ifs the first part that the horse will eat. As he is eating the outer parts of hay, the hay on the inside will be cooling down.
If you horse doesn't like warm hay then leave it to cool down.
Some horses and ponies even prefer eating warm hay to chewing on cold wet hay.
Some horse owners improvise with their own methods of steaming by placing hay in a dustbin and pouring a kettle of boiling water or the hay. The lid is then placed on the dustbin and the hay left for about 20 minutes.
Although this may appear to work be aware that unless the temperature in the dustbin remains high enough for long enough it can provide a perfect breeding ground for bacteria to develop - a warm, damp environent is a gift to bacteria. A hay steamer will keep the hay steaming at a constant high temperature and avoid this danger.