Thomas Kwa comments on Do you believe in hundred dollar bills lying on the ground? Consider humming

• I don’t know what you mean by “total amount” because ppm is a concentration, but that tweet’s interpretation agrees with mine.

The wording ppm*hour being a typo for ppm/​hour does not make sense to me because that would be dimensionally very strange. That could mean the concentration increases by 0.11 ppm per hour every hour, but for how long? A single dose can’t cause this increase indefinitely. The only ways that I could see exposure being measured sensibly are:

• ppm * hour (NO concentration of nasal air, integrated exposure over time, it is unspecified whether the concentration is 0.11 ppm for 1 hour or 19.8 ppm for 10 seconds or whatever)

• ppm (NO concentration of nasal air, peak)

• ppm (NO concentration of nasal air, average over the 8 hour interval between doses)

• ppm (concentration of the 0.56ml of nasal spray, so 0.11 ppm would be 0.06 nL or 0.06 µg or something of NO delivered).

• I don’t know what you mean by “total amount” because ppm is a concentration

The spray is clearly delivering a set amount, but describing it in ppm. Since the volume and density of air inside then nose isn’t changing, you can treat the change as a count rather than concentration.

that tweet’s interpretation agrees with mine.

My understanding of the tweet’s model is that [actual released amount] * [8 hours] = 0.11ppm, so [released amount] = 0.11/​8.

I still don’t understand your number. Could you expand the equation behind “If NO is produced and reacts immediately, say in 20 seconds, this means the concentration achieved is 19.8 ppm”?