So - are we getting it or are we not - nicotine

[DVap]

Thanks, Dvap. I've been following your posts, but still wasn't quite clear. This sums it better for me. I also fall in line with your findings. The more of your posts I read the more confused I became. It makes sense, now. Thanks for all your work and bringing it down to a level I can understand.

Thanks TV,

That thread can be a horror to read, if anything's come of it all aside from the purely practical (being able to accurately determine nicotine in e-liquid concentrates without needing a lab), then the ~40% efficiency of vaping is the finding that stands out.

I consider the finding fairly significant for a couple reasons, 1) it puts a number on the amount of nicotine we're getting from e-cigs, and 2) it closely falls in line with the nicotine consumption vapers gravitate to (self-titration) compared against their former analog habit. It has what we scientists like to call "predictive power".

 

[telsie]

I've put up a blog post about my experience with e-liquid strength and quantity versus former analog consumption. What I've found in my own case, and in a surprising majority of vapers I've talked to is that when we "find our own level" for e-liquid, that is the combination of mg and mL vaped per day, the total mg of nicotine used per day is awfully close to 2.5X the nicotine we used to get from analogs.

Any theory on why people seem to require about 2.5x the amount of nicotine from vaping than we used to require from smoking? I'm finding it's true of me too and I'm curious about that. I used to smoke 40 ultra lights per day (.4mg each) giving me about 16mg nicotine. Now I'm vaping about 2ml or so of 18mg per day (plus a few drops throughout the day of 24mg). So I'm probably getting about 40mg nicotine per day. I haven't tracked it all that well yet, but that seems to be what I've settled in to.

 

[vapomike]

I know I'm definitely getting it. I vaped my girlfriends e-cig with no nic. It didn't satisfy me, I took a few puffs off of my e-cig with 24mg juice and felt the nic edge go away. The other day I really had a bad day. I woke up late for work, on the way too work a dog decided it wanted to run out in front of my car I ran off into a ditch (it was a big dog, figured the ditch would do less damage) hit the drain pipe busted the frack out of my rim and tire. Put the spare on, drove back home had my girlfriend take me to work. Showed up an hour late, and we had a load of work to get done that particular day to get the store caught up. Was totally stressing at work because right now money is super tight. Girlfriend who is pregnant, just got fired from the same company I work at for some total bs reason. I think it had too do something with her upcoming maternity leave during the biggest part of the year for the company. Though anyways enough of my venting/whining. I got too work and really wanted a "CIGARETTE" not my 510, I wanted to go out back and have a marlboro maybe 2. Though I just sat at the back desk with my 510 and toked it for a good 30 min and I got over the hardest crave I have had since quitting analogs. So I am pretty confident that nicotine is getting too us vapors just fine or me at least.

Though what spikes my interest is if different people absorb the nicotine from the vapor as well as others. I would imagine so with all the differing viewpoints. One person that smokes 1 pack a day full flavors can get away with 18mg and then another can't get away with 26 mg and has to go to 36 mg and sometimes higher to get off the analogs. Then some people will get queasy from vaping anything higher than 18mg. I think some people's bodies are more adept to adsorb the nicotine from vapor than others.

 

[Heed]

Since my name has come up a few times in this thread, a quick summary of what I've discovered might be useful.

Nicotine delivery: Actually, e-cigs are more efficient than analogs in delivering nicotine. How so? An analog might contain around a gram of tobacco at 1% nicotine. Of the ~10 mg of nicotine present in a full flavor analog, only 1 mg typically gets absorbed, that's 10%. With e-liquid, both my testing (vaping into a cryogenic trap) and empirical evidence (polling vapers on their former analog habits vs their current vaping habits), the percentage is much greater, approximately 40%.

I've put up a blog post about my experience with e-liquid strength and quantity versus former analog consumption. What I've found in my own case, and in a surprising majority of vapers I've talked to is that when we "find our own level" for e-liquid, that is the combination of mg and mL vaped per day, the total mg of nicotine used per day is awfully close to 2.5X the nicotine we used to get from analogs. Example, a vaper used to smoke 30 full flavor (1mg) analogs down to the ..... Analogs provided 30 mg/day of nicotine. The total mg of nicotine vaped per day would need to be 2.5X greater, or 75 mg. This could be gotten from ~4 mL of 18 mg, ~3 mL of 24 mg, or ~2 mL of 36 mg. This empirical 40% lines up well with the trapping test which demonstrated that approximately 40% of the nicotine vaped ended up being found in the trap. You might do the math yourself for your former analog habit vs your current vaping habit. I expect many of you will be surprised.

All that aside, one thing is certain: The oft quoted "only 10% of the vaped nicotine gets absorbed" figure is plain wrong. E-cigs are not placebos.

Doesn't that then put absorption of nicotine via the vapour around 100%? That is, if around 60% of the nicotine in the liquid is lost and doesn't make it into the vapour, then to achieve a 40% absorption rate of the liquid's rated strength the vapour must be delivering 100% of the nicotine it carries into the bloodstream.

The blood levels people have had done don't seem to indicate that level of efficiency since results showed nicotine levels well below what would have been expected from smoking. The people were not maintaining their nicotine levels via vaping at the same level they would have been at from smoking.

I believe you weren't measuring absorption with your trap experiment, but just the amount of nicotine that survives from liquid to vapour. Please correct me if I'm wrong.

The polling data could well be an "acceptable level" of nicotine that users find -- that is, when "finding their level" vapers don't find their old smoking level of nicotine at the 2.5x point, but a lesser percentage of that level that is still enough to satisfy when coupled with mimicry of the smoking action itself.

 

[DVap]

Any theory on why people seem to require about 2.5x the amount of nicotine from vaping than we used to require from smoking? I'm finding it's true of me too and I'm curious about that. I used to smoke 40 ultra lights per day (.4mg each) giving me about 16mg nicotine. Now I'm vaping about 2ml or so of 18mg per day (plus a few drops throughout the day of 24mg). So I'm probably getting about 40mg nicotine per day. I haven't tracked it all that well yet, but that seems to be what I've settled in to.

If I smoke 20 analogs rated at 1 mg, the tobacco company has already done the testing as mandated by the government, and I know I'm getting ~20 mg of nicotine. It doesn't matter that those 20 analogs contained ~200 mg of nicotine. Smoking delivers about 10% of the nicotine present to the inhaled smoke.

A point that I should make here is that I believe we all have a "setpoint" for our nicotine addiction, unique to our individual brain chemistry, and it resists being changed. If an ultra-light smoker starts smoking full flavor analogs, consumption will generally go down to compensate for the over-dosing of nicotine. If a full flavor smoker starts smoking ultra-lights, consumption will generally go up to compensate for the under-dosing of nicotine. I do not particularly believe that higher nicotine consumption than normal will result in a greater level of nicotine addiction, or that tolerance leads to increased usage. Very simply, I believe we all have our unique "addiction level", and we quite unconsciously and expertly maintain it.

Back to the analog/vaping comparison. We had 20 full flavor analogs per day delivering 20 mg of nicotine per day. I've found that we need to vape 2.5X the nicotine, or 50 mg/day, so we might vape ~2.5 mL of 20 mg or ~1.5 mg of 36 mg. We're putting ~ 50 mg of nicotine onto the atomizer coil because of that 50 mg, only 40% or 20 mg of nicotine makes it into the vapor and into our bodies. So by vaping 50 mg of nicotine per day, we are delivering 20 mg of nicotine per day to our bodies.

Hope this helps!

 

[DVap]

Though what spikes my interest is if different people absorb the nicotine from the vapor as well as others. I would imagine so with all the differing viewpoints. One person that smokes 1 pack a day full flavors can get away with 18mg and then another can't get away with 26 mg and has to go to 36 mg and sometimes higher to get off the analogs. Then some people will get queasy from vaping anything higher than 18mg. I think some people's bodies are more adept to adsorb the nicotine from vapor than others.

You might consider the level of nicotine addiction in the individual. If a vaper's analog habit was 2.5 packs of full flavor (1 mg) per day, then 50 mg is that person's addiction setpoint. For vaping to balance a 50 mg analog habit, then 50 mg x 2.5 or 125 mg of nicotine must be vaped. That's about 3.5 mL of 36 mg juice needed.

On a per puff basis, it gets interesting. If an 1 mg analog smoker takes 10 good solid puffs from an analog, then 0.1 mg per puff of nicotine is being delivered. I've done some testing (precise before/after weighing of e-cigs) and a good solid puff (5 sec) from an e-cig can vaporize 5 micoliters of liquid. For a 36 mg liquid, this represents 0.18 mg of nicotine. But we have to divide it by 2.5 to account for efficiency, so that 0.18 mg vaped only delivers 0.072 mg to the body. This suggests that on a puff per puff basis,
a full flavor smoker would need a 50 mg liquid to get the same nicotine as with an analog, and would still have to take long 5 sec puffs to get it.

The idea that 50 mg liquid is appropriate for some vapers flies in the face of "conventional wisdom" about vaping, but the more I test, and the more vapers I talk to, the more convinced I become that "conventional wisdom" is wrong. Puff per puff, former full flavor smokers desire a 50 mg liquid, former light smokers desire a 36 mg liquid, and former ultralight smokers desire a 24 mg liquid.

 

[DVap]

Doesn't that then put absorption of nicotine via the vapour around 100%? That is, if around 60% of the nicotine in the liquid is lost and doesn't make it into the vapour, then to achieve a 40% absorption rate of the liquid's rated strength the vapour must be delivering 100% of the nicotine it carries into the bloodstream.

The blood levels people have had done don't seem to indicate that level of efficiency since results showed nicotine levels well below what would have been expected from smoking. The people were not maintaining their nicotine levels via vaping at the same level they would have been at from smoking.

I believe you weren't measuring absorption with your trap experiment, but just the amount of nicotine that survives from liquid to vapour. Please correct me if I'm wrong.

The polling data could well be an "acceptable level" of nicotine that users find -- that is, when "finding their level" vapers don't find their old smoking level of nicotine at the 2.5x point, but a lesser percentage of that level that is still enough to satisfy when coupled with mimicry of the smoking action itself.

Yes.. that would put the vapor absorption of nicotine very high. The surface area of the interior of our lungs is on the order of ~100 square meters according to a quick search. That's a lot of surface area.

As far as maintaining levels versus analogs, please see my previous post detailing the e-liquid strength I believe is required to maintain a puff per puff balance between smoking and vaping. It is surprisingly high (24 mg for ultralights, 36 mg for lights, and 50 mg for full flavor).

 

[Heed]

Yes.. that would put the vapor absorption of nicotine very high. The surface area of the interior of our lungs is on the order of ~100 square meters according to a quick search. That's a lot of surface area.

As far as maintaining levels versus analogs, please see my previous post detailing the e-liquid strength I believe is required to maintain a puff per puff balance between smoking and vaping. It is surprisingly high (24 mg for ultralights, 36 mg for lights, and 50 mg for full flavor).

Surface area of the lungs notwithstanding, the blood work we have seen so far seems to indicate much lower levels of nicotine than a smoker would have. Those who have "found their level" (presumably around the 2.5x point) are not seeing that translate into actual blood levels, so I just don't see how this can be if the absorption level of nicotine from the vapour is near 100%.

 

[Sevenchan]

I'll chime in to say that I KNOW I'm getting nicotine from my e-cig. When I chain-vape too much, I get the exact same "gritty, tight" feeling in the bottom of my throat that I used to get from smoking cigarettes that were too strong for me.

I was an ultra-light smoker -- about 25-30 0.3 mg cigarettes a day -- which would be 8-9 mg of nicotine. I've settled on vaping 15 mg or 18 mg, about 4 ml a day. That should be 60 mg of nicotine. I figure I'm absorbing about 20% of it, if that. Still, like I said, I still overdose sometimes, and when I get a craving and vape, I feel relaxed and cheered up. It's there, it's working

I have NO intention of quitting nicotine, ever, by the way. Why would I want to quit something that helps me cope with life? The whole point of e-cigs for me is that I can carry on smoking without feeling like ****.

 

[TropicalBob]

Dvap, your posts are terrific. I've followed you in the other threads. Chemistry aside for a moment, the only bottom line for me is blood nicotine level and per puff nicotine delivery.

When e-smoking can move my blood nicotine level to what I had as a former 30-a-day cigarette smoker .. whoopee. Until then, I'm nicotine deprived as an e-smoker and get what I need from snus, nasal snuff, and disssolvables used at the same time as I vape 36mg liquid.

 

[LameBMX]

If I smoke 20 analogs rated at 1 mg, the tobacco company has already done the testing as mandated by the government, and I know I'm getting ~20 mg of nicotine. It doesn't matter that those 20 analogs contained ~200 mg of nicotine. Smoking delivers about 10% of the nicotine present to the inhaled smoke.

A point that I should make here is that I believe we all have a "setpoint" for our nicotine addiction, unique to our individual brain chemistry, and it resists being changed. If an ultra-light smoker starts smoking full flavor analogs, consumption will generally go down to compensate for the over-dosing of nicotine. If a full flavor smoker starts smoking ultra-lights, consumption will generally go up to compensate for the under-dosing of nicotine. I do not particularly believe that higher nicotine consumption than normal will result in a greater level of nicotine addiction, or that tolerance leads to increased usage. Very simply, I believe we all have our unique "addiction level", and we quite unconsciously and expertly maintain it.

Back to the analog/vaping comparison. We had 20 full flavor analogs per day delivering 20 mg of nicotine per day. I've found that we need to vape 2.5X the nicotine, or 50 mg/day, so we might vape ~2.5 mL of 20 mg or ~1.5 mg of 36 mg. We're putting ~ 50 mg of nicotine onto the atomizer coil because of that 50 mg, only 40% or 20 mg of nicotine makes it into the vapor and into our bodies. So by vaping 50 mg of nicotine per day, we are delivering 20 mg of nicotine per day to our bodies.

Hope this helps!

I was going to reply to telsie's post myself. But yours will actually do better. I always thought they stated the actual nicotine amount in the cigarette? It seems since the cigarette is a constant. There are X grams of tobacco which contain an average of Xmg nicotine per Xg of tobacco leading to Xmg per cigarette. We all know body chemistries are different, how would they mandate cigarettes report the amount of nicotine that enters one's blood stream when they do not know how fast it is going to be absorbed, and how much is going to be absorbed.

Now I understand an average, you quote 10%, but how does one take an average and compound that with an average over such small quantities and expect any real sort resolution to the results. The concentration of nicotine varies within the tobacco leaf itself. They have no way to accurately determine the actual nicotine level in a cigarette. But they can determine a fairly close approximation of how much nicotine is in a cigarette. And then to take that approximation and be like, your body see's this much nicotine. That is scientifically irresponsible.

Lastly, given that 100g of tobacco yields about 3g of nicotine (discovered through research of nicotine purification, I can link if requested). or approximately a 6.5oz can of rolling tobacco (A little more than a carton from experiences as a smoker) this comes out to be about 15mg per cigarette.

========== <- skid marks
FTC has testified about its methodology in determining the levels of tar and nicotine in cigarettes:

http:www.ftc.gov opa 2007 11 tar.shtm

So the FTC admits that having a machine smoke and measuring what is inside the machine is not good. Mind you the FTC measurements are what is available to the lungs to be absorbed into the blood stream.

I hate getting thrown for a loop like that lol. I was wrong for the right reasons.

So how can we accurately determine what our lungs see in different instances between smoking and vaping?

 

[DVap]

I was going to reply to telsie's post myself. But yours will actually do better. I always thought they stated the actual nicotine amount in the cigarette? It seems since the cigarette is a constant. There are X grams of tobacco which contain an average of Xmg nicotine per Xg of tobacco leading to Xmg per cigarette. We all know body chemistries are different, how would they mandate cigarettes report the amount of nicotine that enters one's blood stream when they do not know how fast it is going to be absorbed, and how much is going to be absorbed.

Now I understand an average, you quote 10%, but how does one take an average and compound that with an average over such small quantities and expect any real sort resolution to the results. The concentration of nicotine varies within the tobacco leaf itself. They have no way to accurately determine the actual nicotine level in a cigarette. But they can determine a fairly close approximation of how much nicotine is in a cigarette. And then to take that approximation and be like, your body see's this much nicotine. That is scientifically irresponsible.

Lastly, given that 100g of tobacco yields about 3g of nicotine (discovered through research of nicotine purification, I can link if requested). or approximately a 6.5oz can of rolling tobacco (A little more than a carton from experiences as a smoker) this comes out to be about 15mg per cigarette.

========== <- skid marks
FTC has testified about its methodology in determining the levels of tar and nicotine in cigarettes:

http:www.ftc.gov opa 2007 11 tar.shtm

So the FTC admits that having a machine smoke and measuring what is inside the machine is not good. Mind you the FTC measurements are what is available to the lungs to be absorbed into the blood stream.

I hate getting thrown for a loop like that lol. I was wrong for the right reasons.

So how can we accurately determine what our lungs see in different instances between smoking and vaping?

Wow.. good points throughout. As far as tobacco and nicotine content, it varies. For common nicotiana tabacum, 1% - 3% is common, with the blending generally putting it down toward the lower end of the range. On the other hand nicotiana rustica is loaded, pushing 10% at the stronger end of the range (though it's not commonly used in cigarettes). Your numbers for tobacco are certainly within the range that might be seen in the real world.

As far as what we get from an analog, it is protocol based, and the results are only as good as the protocol and only as good as our smoking behavior approximates the protocol. While a full flavor analog may be rated at 1 mg of nicotine, depending upon how aggressively it is smoked, I can imagine anywhere from 0.5 - 2 mg being absorbed, and that depends to some degree on depth of inhalation, time held, etc. There is a literal cluster-you-know-what of variables at work.

You are absolutely correct about the uncertainty, and problem is simply that while testing protocols generally attempt to model based on reality, reality is free to express a wider range of conditions, and thus feels no compulsion to adhere itself to testing protocols.

I would argue against the assertion that those who have found their level for vaping (mg and mL) necessarily have lower blood cotinine levels than when they smoked.

I want to know what mg and mL of e-liquid will produce the same blood cotinine levels as a pack of reds at the same time of day given say 2 days to equilibrate.

I've not looked at much data myself comparing blood cotinine for an individual vaping a certain mg and mL per day versus that same individual smoking a certain number of analogs at a certain strength. If someone could point me to research that compares this, I'd sure appreciate it so I could dissect it. If the testing (for example) has the subject smoking a pack per day of marlboro red's versus vaping 16 mg liquid at 1.5 mL per day, I can almost guarantee the blood cotinine level will be much higher for the tobacco, likely by a factor of around 2, because very simply, a 16 mg e-cig can't keep up with a full flavor cigarette.

When I see a blood cotinine comparison of 1.5 mL of 36 mg/day versus a pack a day of reds, then I'll be fascinated by the result... because I expect the blood cotinine levels to be very similar.

 

[telsie]

Back to the analog/vaping comparison. We had 20 full flavor analogs per day delivering 20 mg of nicotine per day. I've found that we need to vape 2.5X the nicotine, or 50 mg/day, so we might vape ~2.5 mL of 20 mg or ~1.5 mg of 36 mg. We're putting ~ 50 mg of nicotine onto the atomizer coil because of that 50 mg, only 40% or 20 mg of nicotine makes it into the vapor and into our bodies. So by vaping 50 mg of nicotine per day, we are delivering 20 mg of nicotine per day to our bodies.

Hope this helps!

That makes perfect sense. Thank you.

I always thought they stated the actual nicotine amount in the cigarette? It seems since the cigarette is a constant. There are X grams of tobacco which contain an average of Xmg nicotine per Xg of tobacco leading to Xmg per cigarette.

I was always under the impression that the stated nicotine levels in cigarettes were how much you get from them, not how much are in them at the start.

 

[DVap]

I was always under the impression that the stated nicotine levels in cigarettes were how much you get from them, not how much are in them at the start.

True.. but based on a smoking machine protocol. YMMV.

 

[Stubby]

Dvap, your posts are terrific. I've followed you in the other threads. Chemistry aside for a moment, the only bottom line for me is blood nicotine level and per puff nicotine delivery.

When e-smoking can move my blood nicotine level to what I had as a former 30-a-day cigarette smoker .. whoopee. Until then, I'm nicotine deprived as an e-smoker and get what I need from snus, nasal snuff, and disssolvables used at the same time as I vape 36mg liquid.

Have to agree with you TB. Here are some blood nicotine levels

http://www.e-cigarette-forum.com/forum/nicotine/30623-blood-test-lab-results-nicotine-levels.html

Blood nicotine levels are on the low to very low side, and this using 3 mm of 36 mg liquid. Not very confidence inspiring.

I certainly do appreciate the work that Dvap has put in, but I do have some problems with the x2.5 theory. You seem to have cherry picked your successes, while ignoring the failures. To many people out their chain vaping 36 mm and still having problems. I would say that the x2.5 works for some people, but making a blanket statement that this is the formula that works is stretching it.

 

[Heed]

Have to agree with you TB. Here are some blood nicotine levels

http://www.e-cigarette-forum.com/forum/nicotine/30623-blood-test-lab-results-nicotine-levels.html

Blood nicotine levels are on the low to very low side, and this using 3 mm of 36 mg liquid. Not very confidence inspiring.

I certainly do appreciate the work that Dvap has put in, but I do have some problems with the x2.5 theory. You seem to have cherry picked your successes, while ignoring the failures. To many people out their chain vaping 36 mm and still having problems. I would say that the x2.5 works for some people, but making a blanket statement that this is the formula that works is stretching it.

That's the same link I supplied in my earlier post http://www.e-cigarette-forum.com/fo...-we-getting-we-not-nicotine-3.html#post675015 and the test subject (happily) posted directly following that post saying his levels were at about 15% of what would be expected: http://www.e-cigarette-forum.com/fo...-we-getting-we-not-nicotine-3.html#post675043

And there's this http://www.e-cigarette-forum.com/fo...daily-docket-sheet-update-243.html#post677284 post, that I also linked to in that earlier post of mine, from someone who took part in a clinical trial:

The conclusions from the study were basically that ecigs successfully inhibit cravings for smoking while not appearing to deliver as much nicotine. They took blood every 15 minutes for one sitting where i had to smoke analogs and one sitting where i got to smoke an ecig (crappy Crown7, worst e-cig i've ever used). They also monitored heart rate, blood pressure, and a bunch of lung tests (capacity, CO2, NO3, etc). E-cig day had much lower blood nicotine content, a small HR and BP increase, and almost no deviation from the control run on the lung tests when compared with the analog day.

 

[thunderhead777]

I know that being without a working PV for almost a month now (and not returning to analogs while I wait...and wait...and wait...and wait....and wait...and wait...and wait for my new PV order to arrive -- almost 2 weeks now) that I am constantly irritable and either overly hypertensive or ridiculously tired....or both at the same time.

Nicotine definitely gets into my system when I vape. I don't know how anyone could possibly go through 3ml in one day of juice. I bought a 50ml bottle from Parked a while back and it lasted me over a month. But then again I only like to vape for a few minutes when I first wake up in the morning, just before going to work, and for a little longer at the end of my work day.

It sure would be nice to get my order...

 

[Stubby]

The conclusions from the study were basically that ecigs successfully inhibit cravings for smoking while not appearing to deliver as much nicotine. They took blood every 15 minutes for one sitting where i had to smoke analogs and one sitting where i got to smoke an ecig (crappy Crown7, worst e-cig i've ever used). They also monitored heart rate, blood pressure, and a bunch of lung tests (capacity, CO2, NO3, etc). E-cig day had much lower blood nicotine content, a small HR and BP increase, and almost no deviation from the control run on the lung tests when compared with the analog day.

Which begs the question, how much is enough?

As has been stated, the set point for what levels of nicotine we need is very likely set, varies from individual to individual, and doesn't appear to change. Even it we get more then we need at times, we don't appear to increase our tolerance or need for nicotine, even after many years of smoking. So perhaps some people are getting enough, though likely on the low end of it to stave off the demons. For others, with a bit higher nicotine needs it's not doing it.

I have big problems with the one size fits all approach.

 

[four2109]

I don't find the 2.5 number off at all. People smoke differently. I smoked 2 packs a day of full flavor kings, but I always had one going. Many burned up in the ashtray while I was typing, surfing... Compared to a 1 pack a day friend who smoked only on breaks or while driving, never smoked while doing other things, stopped everything to SMOKE. She would finished a "100" way before I finished a "king". We may very well have absorbed the same amount of nicotine. Based on the 2.5 calculation, I probably only really smoked a pack a day. Just cost me twice as much!

 

[DVap]

I certainly do appreciate the work that Dvap has put in, but I do have some problems with the x2.5 theory. You seem to have cherry picked your successes, while ignoring the failures. To many people out their chain vaping 36 mm and still having problems. I would say that the x2.5 works for some people, but making a blanket statement that this is the formula that works is stretching it.

Will have to look at those test results.. thanks.

Of course this is not "the formula", it is simply one that has thus far proven to predict around 75% of the vapers from whom I've received input. I'm quite interested in the other 25%, for instance I was talking with TropicalBob.. he seems to be one of the folks who doesn't fit into the model, appearing to use perhaps 1.5 times what the model would suggest.

I do, perhaps naturally, prefer to point out the success rate of my model at prediction, but to ignore or attempt to brush under the carpet that (so far) 25% who aren't fitting would be bad science on my part. Currently, unless the "this model doesn't work" crowd starts to feed me data in greater numbers, I can say that more likely than not, the model works... and here's the important part.. based on my experience.

I think the usefulness of a model such as mine is not so much in trying to "nail down all possibilities", that would be a fool's errand, because it can't be done. the usefulness may be more in having a starting point where one could, for example, recommend a starting point to someone new to vaping, "Oh, you smoked two packs of reds per day? Try the 36 mg, and see if maybe 3 mL doesn't do the trick for you."