Obligatory precaution

On the basis of obligatory precaution, allowing thick dust to reach one's throat makes one's fast void.whether the dust is of something which is halal to eat, like flour, or of something which is haram to consume like dust.

Allowing thin dust to reach one's throat will not invalidate the fast.

As an obligatory precaution, a person who is observing fasts, should not allow the smoke of cigarettes, tobacco, and other similar things to reach his throat.

If a person forgets that he is fasting and does not exercise care, or if dust or any other similar thing enters his throat involuntarily, his fast does not become void.

Immersing one's head in Water

If a fasting person intentionally immerses his entire head in the water, his fast is known to be void, even if the rest of his body remains out of water.

But if a person immerses half of his head in the water once, and the other half the second time, his fast is not affected.

If a fasting person falls into the water involuntarily, and his entire head goes into the water, or if he forgets that he is fasting and immerses his head in the water, his fast is not affected.

If a person throws himself into the water thinking that his entire head will not go down into the water, and water covers his entire head, his fast remains in order.

If a person throws himself into the water thinking that his entire head will not go down into the water, and water covers his entire head, his fast remains in order.

If a person forgets that he is fasting and immerses his head in the water, and he remembers under the water that he is fasting, it is better that he takes his head out of water at once.