How Does a Breathalyzer Work?

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How does a breathalyzer work?

Adey Hill:

The breathalyzer or intoxilyzer is a modified IR spectrometer.

Before I get into that, let's talk about alcohol and how it gets into the blood and breath: Alcohol is a general name for a group of organic compounds. Ethanol, the alcohol we consume in alcoholic beverages, is a relatively small molecule. As such it is easily absorbed through the stomach into the blood. Alcohol is volatile and your body is warm. Each time you breathe, a small amount of the alcohol in your blood vaporizes and is passed into the alveoli in your lungs and passed out of your body. The more alcohol you have consumed, the greater the amount that passes out.

Organic compounds absorb infrared radiation (IR) at different wavelengths and have an IR signature. The infrared (IR) spectrometer in the intoxilyzers is calibrated so that it is at the wavelength that ethanol absorbs it.

When you blow into an intoxilyzer, the breath you expire passes into a sample chamber and if you have been drinking then so will some of the alcohol that has passed from your blood to your breath. In the case of the Lion Intoxilyzer 6000s produced by Lion Labs, the machine starts sampling the breath immediately as it starts to enter the chamber and does so 37 times per second. The machine continues to monitor this until you blow a consecutive reading for three seconds. This is so that it is taking the reading from the deep lung air, where the greatest concentration of alcohol is. Once this is achieved the machine will register that a satisfactory sample has been taken. It will then purge itself and move to the next stage (either a second sample or a calibration check).

The breath in the sample chamber is surveyed by a beam of infrared radiation (there is an IR detector behind the chamber). The machine knows the amount of IR that was fired at the chamber and the detector calculates how much has been absorbed. Some clever math works out how many micrograms of alcohol are present in 100 ml of breath. This reading is then displayed.

Some other factoids about the machines: breathalyzers can detect other substances such as methanol, isopropyl alcohol, or acetone. If these are present in sufficient quantities, the machine will register them as an interfering substance and your sample will not be deemed satisfactory.

The breath tube (which you blow into via a single use mouthpiece) is preheated to a specific temperature to ensure that the samples conform to Boyle's law and are consistent and accurate every time.

The machines can detect mouth alcohol. If you have recently consumed alcohol or used an alcohol-based mouthwash, the machine can detect it. The intoxilyzer starts sampling as you start to blow, so it will detect a high concentration of alcohol present at the start of the process, followed by a downward slope (on a graph); this spike tells the machine that there was more alcohol present at the beginning of the sampling process than at the end, and that this must be due to the presence of mouth alcohol.

You cannot cheat or defeat the intoxilyzers by trying to blow down the sides of the mouthpiece, putting your tongue over it, or putting some kind of catalyst (like a copper coin) in your mouth first. The only way to beat it is to not drink and drive!

This post originally appeared on Quora. Click here to view.

Why Choosing the Second Cheapest Wine on the Menu Isn't Such a Good Idea

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iStock.com/kupicoo

For those whose knowledge of wine is limited to whatever lessons they picked up while watching Sideways, it can be tempting to order a glass of the second-cheapest vino on the menu at bars and restaurants. According to this line of reasoning, you don't want to look cheap by choosing the least expensive wine—but at the same time, it doesn't make sense to order a pricey vintage red if you're not the kind of wine enthusiast who confidently throws around terms like "mouth-feel" and "hints of oak" and would therefore understand and appreciate the difference in quality.

Although this wine hack is widely observed, the Skimm points out why it isn't such a sound method. For one, restaurants are well aware of this customer habit and might even use it to their advantage by taking a bottle they're looking to get rid of and placing it in the second-cheapest slot. That could mean that you're getting a not-so-great bottle of wine and may have been better off ordering the cheapest one on the list.

"I can confirm that restaurants will occasionally reprice a wine that they need to move to make it the second-cheapest spot on the menu," sommelier Kirsten Vicenza tells Atlas Obscura. "It sells!"

And then there are the markups. According to Wine Enthusiast, the cheapest wines tend to have the highest markups, so while your bill may be lower than if you had ordered a top-tier wine, you're also getting the lowest value. The magazine recommends ordering a wine somewhere in the middle—perhaps the third or fourth cheapest wine—to get more bang for your buck.

This isn't a "hard and fast rule," though, as VinePair notes. Sommeliers will sometimes lower the price of a lesser-known wine to encourage customers to try it. If you're unsure what to order, it never hurts to ask for a recommendation.

[h/t Skimm]

How Much a Pint of Beer Will Cost You Around the World

Peter Macdiarmid/Getty Images
Peter Macdiarmid/Getty Images

After updating your passport and packing your suitcase, there's one last thing you should check before going on vacation: How much will a pint of beer cost at your destination?

Just as food and lodging varies in price from country to country, so does beer. To make sure you're prepared for whatever you find on beer menus abroad, The Wall Street Journal has compiled the average cost of a pint of beer in major cities around the world, using data from the travel site OMIO's Beer Price Index.

According to this data, Hong Kong is home to the most expensive brews, with bar patrons shelling out an average of $10.86 per pint in the city. Beer prices don't look much better in the U.S., where the average pint of beer at a bar costs $8.97 in both Miami and New York.

To find cheap beer, you need to head to Eastern Europe or South Asia. A pint costs an average of just $2.22 at bars in Bratislava, Slovakia, the cheapest of any of the cities the WSJ looked at. In Delhi, India, you can get a pint for $2.31, and in Kiev, Ukraine, you can find one for $2.36.

If you're factoring beer prices into your future vacation plans, check out the five most expensive pints and five least expensive pints by city below. And for a different way to look at international beer prices, here's how much beer you can get for $1 around the world.

Cities With the Most Expensive Pints of Beer

1. Hong Kong: $10.86
2. Geneva, Switzerland: $10.77
3. Tel Aviv, Israel: $9.53
4. New York City: $8.97
5. Miami: $8.97

Cities With the Cheapest Pints of Beer

1. Bratislava, Slovakia: $2.22
2. Delhi, India: $2.31
3. Kiev, Ukraine: $2.36
4. Ho Chi Minh City, Vietnam: $2.58
5. Kraków, Poland: $2.70

[h/t The Wall Street Journal]

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