There is no formula or exact conversion from a single TAC value to a single % BAC value. This is because it takes a greater amount of time for the alcohol you drink to travel through your body and out to your skin layer than it does for alcohol to get into your bloodstream. TAC values are best reviewed collectively over time, as they will rise and fall in a bell shape. Looking at TAC values over 30 minutes or greater is most informative. To estimate % BAC values, at least 30 minutes of TAC data must be collected.
In terms of general patterns of how TAC values can be correlated with drinking events, it’s important to consider the stage of your drinking session. You should consider whether you are just starting to drink or actively drinking vs when you have stopped drinking and are sobering up.
For when you begin to/are actively drinking, if your average TAC over 30 minutes is between 0 - 30ug/L, you might be in a sober/lower drinking session. If your average TAC over 30 minutes is between 30 - 100ug/L, you might be in a more moderate drinking session. If your average TAC over 30 minutes is greater than ~100ug/L, you might be heading into, or out of, a higher drinking session. Please remember there is a time delay between your % BAC signal and the Skyn TAC signal*.
*PLEASE NOTE - all of these values are APPROXIMATE. Personal TAC values are variable depending on how tightly you wear your Skyn, how active you are (how much your wrist is moving around), what pace you are drinking, your personal body composition/metabolism, and the environment you are in. Skyn is very sensitive to environmental alcohol.
For when you are sobering up, the values of your TAC will fall depending on how much alcohol you have consumed, and it is possible for your TAC values to remain positive well after your % BAC has returned to sober/low values. Please review the falling phase of your TAC data over the course of 1 or more hours.
Sample TAC Drinking Curves (TAC ug/L)
- In the instance of moderate drinking sessions, such as two or so standard drinks, you might see a curve like below. Note this is a 24 hour (1 day) time period, and the TAC values in ug/L are on the right side. The TAC values in this curve peak around ~80 ug/L and the TAC signal rises and falls over the course of the evening.
- In the instance of a higher drinking session, you might see a curve like below. Again, note this is a 24 hour (1 day) time period, and the TAC values in ug/L are on the right side. The TAC values in this curve peak around ~150 ug/L and the TAC signal again is a solid bell curve shape.
Sample Environmental Signal (TAC ug/L)
BACtrack Skyn has a sensor that is highly sensitive, and can detect ethanol that may be present just in the surrounding environment. Below is a sample of how this might look in your app.
- In the screen shot below, the app is showing the last last 6 hours of data. Around 12:00pm, there was a small TAC signal, which only rose to about 15ug/L and very quickly dissipated. This is an example of a small environmental disturbance like lotion, sunscreen or other ethanol containing product being near the Skyn.
