I actually only needed the volumetric farts of about 15 hamsters.
However, I thought it’s not realistic to have them all fart at the same time, so I kept buying more.
Eventually it was a big enough group that it seemed more statistically plausible that 15 of them farted in unison.
I feed them beer and cheese and beans to increase the hypothetical flatulence interval of each hamster.
Also I have found, adding “I don’t know, maybe something startled them and some of them… Went off” helps. I could buy a few more hamsters instead, but times are hard.