I'm not sure I follow on how I'd be under the REL if my vaping style remained as noted above. If I hit 4 ppb with 25 puffs across one hour, that'd be 8 ppb in two hours, which would be 3 ppb over the REL of 5 ppb as per NIOSH. If I've hit 8 ppb in two hours, then technically I'm already over the REL which is based on an eight-hour work day.
Oh, I see. This is something really easy to get tripped up on. Like I said, ppb is a
concentration, not a hard amount. Vaping 4 ppb in 1 puff is 4 ppb of exposure for that puff, vaping 4 ppb over 1 hour is 4 ppb exposure for that hour, vaping 4 ppb over 8 hours is 4 ppb exposure for that 8 hours. The recommendations are for the average ppb you get over an 8-hour period (they assume you won't expose yourself beyond that 8 hours for the rest of the day). So you could be inhaling, say, 8 ppb for 4 hours, and then no exposure at all for the next 4 hours, that would be a 4 ppb time-weighted exposure. Or you could be inhaling 8 ppb once every 4 breaths for 8 hours, and that would be a 2 ppb time-weighted exposure.
This is why they also give a recommended limit for short term high exposures, and say you shouldn't be exposed to levels as high as 25 ppb for any longer than 15 minute periods. That way workers or employers won't assume that they can get away with 1000 ppb for a while, as long as they go breathe fresh air for the rest of the day, because acute exposure could still be a hazard.
As for the calculations, would 250,000 ppb not be correct for 10ml of e-liquid using 5% flavoring?
- 5% of 10ml = .5ml flavoring
- 0.05% of .5ml = 0.00025 = 0.025%
- 0.025% = 250,000 ppb = 250 ppm
You just missed the part where you have to divide by the 10 mL to get the percentage. If I had a dime for every time I've done that...
- 5% of 10ml = .5ml flavoring
- 0.05% of .5ml = 0.00025
- 0.00025/10 = 0.000025 = 0.0025%
- 0.0025% = 25,000 ppb = 25 ppm
I wish we could get better numbers on concentrations too. Some of TFA's flavors list diacetyl & co as 1-10%, and that's way too much of a range for me to really decide whether they are tolerable levels or not.
I'll see if I can put together a spreadsheet sometime this week to calculate the actual ppb being vaped based on concentration of chemical(s) in a flavor, concentration of the flavor in the final blend, and how fast someone goes through a mL of liquid. That seems like it could be useful for discussing exposure levels if nothing else.