Lets work this out once and for all...
On average a uman produces 0.5 litres of gas per day devided by the average of 14 farts per day, (http://www.heptune.com/farts.html)
This equates to each fart being around 0.36 litres.
The duration of each fart is about 0.8 seconds (round up to 1 second on average)
That means, if you where to continualy fart all day, every second, that would be 31104 litres of gas per day.
Now times that by a year is 113 52960 litres a year, times that by 6 is 681 17760 litres + 9 months 8514720 = 76632480 litres in total of gas.
Now if we look at the breakdown of what type of gas is emitted...
Oxygen, Nitrogen, Carbon Dioxide
Now this will surprise you, according to Dr James L.A. Roth, author of Gastrointestinal Gas( Ch. 17 in gastroenterology V.4 1976) Most humans do not produce methane in their farts surprised me too) so therefore, the only flamable eliment would be oxygen.
It transpires that only a small proportion is oxygen, the majority is made up of Nitrogen, it all depends on how long you hold a fart dictate how much nitrogen is in it.. the longer you hold it.. the more is obsorbed. Therefore a nervous person who swallows more and has a fast digestive system will produce more oxygen than the opposite. Also some of the bacteria that generate farts, again rlease nitrogen.. not methane.
On a proportion, Oxygen accounts for just 2% of the 0.36 litres. so that again works out over 6 years at 0.007 litres per fart equated to 1512 litres a day = 3311280 over 6 years + 9 months = 3,725,190 litres for the duration
so if we look at an explosion of 745 pressurised cylinders (o2 bottles) which contain 5000 litres of O2, this equates to around 3,700,000 litres. Each tank when released gives off a fireball of about 40 feet so times that by 745, you get a fireball of just over 33,000 feet
...so if you were to fart, non stop.. for 6 years and months.. although the energy would not be the same as oxygen burns almost instantly.. you would have a pretty impressive fireball!! Don't forget, this wouldn't be a nuclear reaction it would be an energy release so on par for par the answer is no.. but you would have a spectacular explosion.
Hope that helps.