What is a Survival Unit (SU)?
Many emergency kits out in the market today claim they have the supplies needed for a number of days, but in reality, they don't. According to FEMA:
"a normally active person needs to drink at least 2 liters (1/2 gallon) of water each day."
But in most cases, the water included in many emergency kits falls short. And this shortfall could impact your chances of survival in an emergency situation.
To help you determine what you need when shopping for emergency supplies, you need to understand the concept of a Survival Unit. We will be adding this terminology to all of our product descriptions over the coming months as these calculations, along with our listed preparedness guides for FEMA-approved survival requirements, will help you to understand and compare the products you are purchasing against your plans and needs.
To properly prepare, how should you be thinking about Survival Units?
In the simplest sense, a Survival Unit (SU) is a term that tells you how much of a given product or service will be required in an emergency for one person per day.
A basic SU is "one person/one day."
For example, using the basal metabolic rate (BMR) as a guide, in an emergency situation, we recommend the average adult consume 2400 calories of food per day. Given that, a food bar that provides 2400 calories, it is said to be "1 SU" of food. These values combine as well. Given that an average adult requires 2 liters of water per day, 1SU of water is 2 liters; if you combine that with a 2400 calorie food bar and you can say that you have 1SU of food and water.
What is a "Convertible Survival Unit (Convertible SU)"?
A Convertible SU refers to a product that can be used either for more people or for longer durations. So 3 SU of food is convertible - it can support 3 people for 1 day, or it can support 1 person for 3 days.
Conversely, NON-convertible (fixed) SU must be regarded as designed. So, a disposable mylar sleeping bag is 14 fixed SU, meaning that one person can use it for 14 days before it breaks down, but 14 people cannot use it for 1 day.
In general, SUs are convertible if they are dealing with consumables (batteries, food, water, a box of band-aids) and fixed if they are dealing with non-consumables (beds, hats, jackets, hammers).
Finally, some products have Unlimited SU (uSU), which means that one or the other side of the calculation has no limit.
Examples of this are:
- a hammer will not wear out, so it has unlimited days of use, but can only support a team of 10 people - so it is considered to have unlimited SU for 10 people (uSU-10p)
- alternatively, a loudspeaker system may only run for 3 days before its batteries wear out, but it's loud enough that crowds can hear it. That would have unlimited people and 3 days (uSU-3d).