Do I need to buy a keychain breathalyzer or can I trust myself?

July 15, 2007 1:31 AM

What does a 0.08 BAC feel like? Can I tell on my own, or should I get one of those keychain breathalyzers?

I just got back from a night of drinking where the alcohol was flowing pretty freely for the first part of the night. Around midnight I switched to nonalcoholic drinks, but by last call I was still feeling pretty affected. I checked an online BAC calculator which said I was probably around 0.02 (the legal limit here in FL is 0.08), but I didn't feel okay to drive at all and played it safe.

A while back, someone I knew had a couple (as in two) beers with dinner and was pulled over. He ended up receiving a DUI. I know I can sometimes have a couple beers with food and not feel affected at all. I don't know this person very well, but I would assume that if he didn't feel safe to drive, he wouldn't have.

When I drink, I try to subjectively judge my own impairment, and take into account two tendencies: 1) When drinking, you tend to exaggerate the feeling that you're in control, and 2) You feel more drunk when you leave the bar than when you're in it, due to the contextual nature of our brains.

Because of the vast differences between the numbers and the subjective side, I'm starting to wonder if trusting my instincts is ever good enough.

My question is: what does 0.08 FEEL like to most people? Is it enough that one would generally notice, or so little that you can be over the limit and not even realize it? My first anecdote would seem to indicate that a 0.08 BAC is pretty severe impairment, and the second seems to indicate that it's a very small amount subjectively. If anyone has a good objective test that will judge the level of impairment, please feel free to share. I know they sell keychain breathalyzers, but I'm not sure how accurate they are or whether they're needed - hence the question.

Note that my main concern here is the law. I'm pretty sure I know when I'm able to drive safely enough to get home without endangering myself or others, but I also know how much a DUI would affect my life.

posted by tkolstee to Food & Drink (20 answers total)

As I understand it, BAC doesn't consistently feel the same to different people. There are any number of factors which impact the real impairment caused by alcohol, including weight, genetics, and frequency and type of consumption.

I believe most DUI statutes err on the side of caution. Indeed, the wiki page on alcohol tolerance mentions a study in which only 24% of alcoholics with a BAC of 0.10 displayed clinical signs of impairment. If you're a social drinker, I would suspect that 0.08 feels like a light-to-mid buzz, but the key term here is YMMV.

What were you drinking, out of curiosity? You're a lot more likely to get accurate BAC estimates counting prepackaged drinks (cans/bottles) than mixed drinks. Reminiscing to my college days, I remember occasionally receiving drinks that were basically pure liquor with a hint of mixer. And even with drinks like wine, you'll sometimes get people with an exaggerated definition of "one glass."

Legally, what it comes down to is better safe than sorry. You did the right thing cabbing it when you felt impaired, but your friend (based on your description) is an example of why your own senses may not be enough to keep your record clean. If you are considering getting a breathalyser, then you should probably follow that instinct. It's the only way to be legally sure.
posted by Riki tiki at 2:00 AM on July 15, 2007

Err, I could've sworn I'd put it in the other comment, but IANAL. IANAD. IAN anything relevant to this question besides a fellow human being in good spirits.

Cheers. :)
posted by Riki tiki at 2:21 AM on July 15, 2007

I once had a go on a breathalyzer at the pub where I was drinking. ie. not a police one!

I was heavy in the head, a little dizzy (a definite buzz), quite coherent but I thought the idea of driving in that state was crazy. I certainly wouldn't have backed myself, even accounting for the increased confidence alcohol was meant to instill.

Funnily enough I only blew 0.08. But of course everyone is different.Here in Australia the BAC is 0.05 - so i wouldnt have been able to drive. But I was amazed at how 'close' I was to being legally able to given the state i was in.
posted by TheOtherGuy at 2:22 AM on July 15, 2007

Going back to my DUI enforcement training...


There are any number of factors which impact the real impairment caused by alcohol, including weight, genetics, and frequency and type of consumption.

Weight, gender, how much you're drinking, the time elapsed, and even whether you're drinking on an empty stomach or not will affect your BAC.

.08 in most states is a per se law, you can still get a DUI with a lower BAC if the officer can prove that you're ability to operate a motor vehicle is impaired. Career drinkers build up a tolerance so that they feel normal at higher BACs then people who only drink occasionally. People who rarely drink may feel "drunk" at a BAC as low as .04. That being said, it is always a good idea NOT to drive if you've been drinking. Period.

As far as keychaid breathalyzers...they're great for shits and grins, but I wouldn't base a decision to drive on them. The most accurate way to determine BAC (besides a blood sample) is an infrared machine (which virtually every police agency has). Bars that have breathalyzer machines in them really shouldn't, as they are inaccurate and this is just simply dangerous.

The average person's BAC declines at a rate of .015 per hour. There are no ways to speed this up. Period.

Again, if you have been drinking, don't drive.
posted by C17H19NO3 at 2:59 AM on July 15, 2007

I'm pretty sure I know when I'm able to drive safely enough to get home without endangering myself or others

I'm pretty sure you don't, just as your friend who thought the same after "a couple of beers" did not. Driving is a dangerous activity even if you are totally sober. It's more dangerous if your abilities are impaired by alcohol, even if you are under the legal limit.

If you have to ask, don't drive. A keychain breathalyzer won't be accurate enough to save you.
posted by grouse at 4:29 AM on July 15, 2007 [3 favorites]

The best approach is to not drive at all if you've been drinking.
posted by winston at 4:52 AM on July 15, 2007

Regarding keychain breathalyzers - an ex-boyfriend of mine had one so that he could see if it was legal for him to drive. One night we were out on the town and he'd had quite a bit to drink so we called a cab and planned on picking up his car the next day. But when the cab was late he used his breathalyzer to check his BAC, and when he found it was only .05 he decided to drive us home.

It was terrifying. We almost hit two vehicles, including a parked RV. When we got back to his place he blew again and this time he checked out as .09. He thought it was hilarious, but since I had sobered up on the way home and experienced the ride more accurately than he had I wasn't as thrilled.

So keep in mind that those little things aren't always accurate. And also remember that even if you aren't legally drunk you could still be impaired enough to get a traffic ticket or cause an accident. It's best to just be careful and call a cab if you've been drinking at all.
posted by christinetheslp at 5:40 AM on July 15, 2007

Thirding the don't drink & drive comments.

If you're driving, don't drink. One drink is enough to impair you. If you do drink, leave the car at home or take a taxi.

Do you really want to be responsible for an accident where someone gets hurt or killed just because you didn't want to spring for the $20 for cab fare?
posted by arcticseal at 5:43 AM on July 15, 2007

As a former owner, I have to nth that those things are not very accurate and should not be relied upon.
posted by a robot made out of meat at 6:03 AM on July 15, 2007

Everybody's different. I've *felt* fine to drive at 0.15. Some people get blitzed on 1-2 drinks, others require many more. If there's any doubt about how you feel, just don't drive.
posted by iguanapolitico at 9:12 AM on July 15, 2007

I feel that the answer to your question is "you can't tell". Everybody above who points out that different people respond differently is correct, but also you probably feel alcohol differently on different occasions. Speaking from personal experience, if I go out and drink 6-8 beers over about 3 hours, sometimes I feel perfectly sober afterwards and sometimes I can barely walk. Whilst what I have eaten might affect my BAC in different occasions, I am sure that my prevailing mood at the time affects my buzz even if my BAC is the same. (Depressed = feel sober; happy = feel drunk).
So I think you can not estimate BAC in the way you want to. Also, don't drink and drive.
posted by nowonmai at 10:01 AM on July 15, 2007

Also, I've read that alcohol only gets into your system at a certain rate. So theoretically, you can drink a ton, stop drinking and whatever amount of time later can actually be drunker than you were right after your last drink.

Sorry, I may not be explaining this exactly right, but basically you could feel fine and then 20 minutes into your drive home you could be in a much more impaired state.
posted by whoaali at 10:15 AM on July 15, 2007

As I understand it, .08 is about the equivalent of one drink per hour per 60kg of body weight. (That's 132 pounds for all you USians.)
posted by number9dream at 10:41 AM on July 15, 2007

This is going to get long-winded and aside from your main question but please read through.

what does 0.08 FEEL like to most people?
It really doesn't matter because like everyone else said, it feels different for everyone. While the answer seems rather bland and obvious, consider what it really means. The law simply defines a DUI by a number and doesn't take any consideration of how you feel at all. You could have 2 quick beers, get in your car to buy to go to the market to buy some chips, and get busted for a DUI or wet reckless simply because the cop happened to pull you over for a busted tail light and smelled your breath. When you left the house you felt fine and maybe your BAC was 0.04 (wet reckless) but by the time you were on the road, the alcohol was starting to set in and your BAC became 0.08 (DUI).

If anyone has a good objective test that will judge the level of impairment, please feel free to share.
As above, even if there was an objective test for level of impairment, it would only help with determining your probability of getting pulled over due to alcohol. That is, while your probability of getting pulled over is significantly higher if you were drunk and swerving than if you were not affected at all and simply forgot to set your right turn signal, in either case, once pulled over, if the cop gets the slightest whiff of alcohol, your probability of getting a DUI or wet reckless is nearly 100%.

If you're a math person, the formula for chance of getting a DUI if you'd had alcohol would be something like this:

%DUI = ( %pulled over for visibly impaired driving + ∑(%all independent reasons why someone has ever been pulled over for anything not related to alcohol) ) * ~100%

So you see, while how much alcohol you've had to drink affects the first part, it has just slight to no effect on the second part. In CA, the second your key goes into the ignition, even if you haven't started the engine, the second part of the formula is already in effect.

I didn't feel okay to drive at all and played it safe
This was a good decision and I'm glad you took a cab. Even living in SF, I used to think it was expensive and a pain to hail a cab, which is rather silly because it's one of the easiest cities to get a cab (relative to the other 99.9% of American cities). I ran the numbers and the DUI costs roughly $10,000 over a lifetime in fines, lost work hours to go to court/dmv/classes/community service, and increased insurance costs. For me, a cab ride costs $15. That means I could have taken 667 cab rides just to break-even with what the DUI cost. Yep, for what the DUI will cost, I could have taken a cab home every single night for 2 years. And the DUI conviction goes on the permanent public criminal record and will never, ever come off.

Of course, this is just the starting point -- if anyone is hurt, your passenger or passengers in another car, it's a completely different league usually starting with months of jail time.
posted by junesix at 11:04 AM on July 15, 2007 [1 favorite]

Have you seen Rob Cockerham's scientific investigation into this issue?
posted by gueneverey at 11:43 AM on July 15, 2007

Have a look at Nolo's book on what to do if you get pulled over. (Search inside on Amazon.) Sleazily enough it's called "Beat your ticket." However, the book has a good explanation of how DUI tickets/stops work. Interesting reading that will hopefully prevent anyone from ever getting on the road with even the slightest suspicion that they might be impaired.

(IANAL, but, "Officer my keychain said I was only a .05" doesn't seem like it would really be very helpful evidence in this situation.)
posted by prettyboyfloyd at 2:22 PM on July 15, 2007

The first thing to go when you drink is your sense of good judgement. There is no way to figure out your BAC based on how you feel.

If you are even remotely worried you may be over, don't even think of driving.
posted by furiousxgeorge at 6:35 PM on July 15, 2007

If you have a high tolerance, you can be cited with a DUI even when you feel completely sober. .08 is going to "feel" different for everyone. It's purposefully low to give cops the ability to use their own judgement. That said, consumer grade BAC readers tend to skew low and generally aren't at all accurate-- see the article here.

You won't get anywhere attempting to calculate your BAC when you drink. Are you willing to take a measuring cup everywhere to make sure you only get 12 ounces of beer (1 "drink") in your plastic cup? Do you plan to ask the bartender exactly how many shots are in that rum and coke, and what proof the rum is? What about telling the waiter to pour you EXACTLY 3.5 ounces of wine? It's just not practical.
posted by almostmanda at 6:47 PM on July 15, 2007

I gave somebody a BAC monitor for Xmas a year or two ago. All day everybody blew into it with random results, like one person blowing 0.05 after 8 drinks, waiting 3 mins then getting 0.12.
They are inaccurate toys. Note that where I live, even the cops can't use them as evidence, if you are caught DUI you are taken for a blood test to determine your BAC.
posted by bystander at 9:17 PM on July 15, 2007

I nth all the things said here, but add the following: In college, I volunteered to get drunk so officers could be trained/tested on field sobriety testing.

I was told by an experienced cop that starting at .05 BAC, a subject's eyes exhibit an involuntary back-and-forth spasm (called horizontal gaze nystagmus or HGN) when looking to the side (with the head stationary). The angle of the onset of HGN assists the officer in estimating a subject's BAC. From here: The examiner looks for three indicators of impairment in each eye: if the eye cannot follow a moving object smoothly, if jerking is distinct when the eye is at maximum deviation, and if the angle of onset of jerking is within 45 degrees of center. If, between the two eyes, four or more clues appear, the suspect likely has a BAC of 0.08 or greater.

I completely agree with others' warnings against drunk driving -- however, I would rely on the HGN test more readily than a Breathalyzer, whose results are (as others have mentioned) iffy.
posted by parilous at 11:33 AM on July 16, 2007