Davening if one is very gassy:
- Shemoneh Esrei: If a person is very gassy, then it is better that he does not daven Shacharis Shemoneh Esrei in this state and he is to rather Daven Tashlumin of Shacharis after Mincha.
- Pesukei Dezimra: Accordingly, one is not to say Pesukei Dezimra with its blessings of Baruch Sheamar and Yishtabach, however, it may be said without its blessings.
- Shema: Even a person who is very gassy must say Brichas Kerias Shema together with Shema within its correct time.
- Wearing a Tallis: One may wear his Tallis while he is releasing gas.
- Wearing Tefillin: If one can hold himself from releasing gas for the recital of Shema, then he is to put on Tefillin with a blessing between the blessing of Habocher Beamo Yisrael and Shema and then immediately remove them. If he can’t withhold himself from releasing gas even for the duration of time it takes to recite the Shema, then he is to recite the Shema without wearing Tefillin.
 See Admur 80:2; Ketzos Hashulchan 18:2