Do Flares Work Underwater and How Long Will It Stay Burning?

Amanda Bullock / December 21,2021

Flares are a great tool to have on hand as they serve a multitude of purposes. Since the beginning of their development, new and innovative ways have been discovered on how to use them in a wide range of scenarios. Whether you need to illuminate a dark area, send a distress signal, or need a defense countermeasure, flares are effective in all these fields.

But do flares work underwater?
Yes, flares will burn underwater for a small length of time before the wick goes out and the flare is done burning. The exact amount of time a flare will burn underwater depends on a variety of factors such as the warmth of the flame and the quality of the flare, although 3-5 minutes is a typical expectancy.
The most common situation to use a flare is when you get the dreaded flat tire on the side of the road and you need a flare to help channel traffic. Flares are a universally understood survival tool and will get the attention of bypassing vehicles as well as help you grasp better control of any desperate situation.
While flares do an excellent job of illuminating in poor weather conditions, roadside emergencies naturally prompt the question of whether or not they are waterproof. Knowing the impact of environmental factors on flares can make the difference in a dire situation turning into a worst-case scenario.
Water Resistance Vs. Waterproof
All flares are water-resistant based on varying degrees. For instance, a roadside chemical flare is water-resistant, however, it is not waterproof. The outer casing of a flare is made of material that is resistant to oxidation. While the flare can be exposed to rainfall, without proper care, the shell can become compromised.
Flare casings typically have a wax or silicone coating applied. This design is intended to impede any water from seeping in and reaching the chemicals. Rain, however, has corroding properties that can disintegrate and destroy a flare through constant wetness. Flares will malfunction and fizzle out if moisture breaches the seal and contaminates the necessary pyrolytic reaction to launch.
Maritime and other submersible flares, on the other hand, do work underwater. Maritime flares have truly raised the bar when it comes to the realm of waterproofing.
The Physics Behind Waterproof Flares
Flames fundamentally require combustible material and an oxidizer to be produced. The chemistry between these two elements is referred to as the combustion of a pyrotechnic formation.
A candle flame for example uses the heated wax as the combustible substance and the surrounding oxygen in the atmosphere as the oxidizer. These two factors are what sustain a candle flame. Getting a flare to work underwater requires the same pyrolytic reaction.
Flares work underwater when oxygen in the water molecules mixes with combustible gases found inside the flare (namely acetylene or hydrogen) and as a result, produce an underwater flame.
Deep-sea divers frequently use flare O-rings on calcium emergency flares. O-rings are hydraulic fittings that are placed on the flare to seal them watertight, essentially making them leak-proof.
Emergency Flare Upkeep
Water damage has the capacity to render a flare ineffective. Although not all flares are waterproof, you will still find that water-resistant flares are just as resilient and will cover most serious circumstances. Taking the necessary steps to protect flares from degrading will ensure optimal performance.
Here are three facts about flare maintenance to ensure safety:
1. Any flare that has been drenched or submerged in water prior to activation should be disposed of.
2. Flares do not have an expiration date but should be frequently checked for rust, cracked casing, or deterioration. Flares that exhibit these flaws and/or are old, should be disposed of in a bucket of water to allow for the breakdown of materials and then thrown away.
3. Where you store your flares, matters. Flares should be stored in a dry, plastic, watertight box. For good measure, you can add a desiccant packet in the storage box for fluctuating temperatures and humidity.
Emergency Flare Classes
The flare industry has manufactured distinct classes of flares. Which type you use is dependent on your situation.

  • Handheld flares: A popular use for roadside emergencies, handheld flares typically burn up to 60 minutes and can be seen up to 3 miles away. These flares burn bright red and are a terrific way to highlight location information to medical air support.
  • Parachute Flares: Commonly used on lifeboats, parachute flares are propelled up to 300 meters when launched and its bright red/orange signal can be seen up to 25 miles away. The slow parachute descent allows for aid to identify the signaler’s location.
  • Smoke Canisters: Smoke canisters are a signaling device that emit smoke for rescue parties to see. They come in varied sizes, colors and smoke capacities. Smoke canisters can also be used as a defense countermeasure against animals or enemies in the form of a shield or distraction.

Flares are an effective way to maintain your safety as well as that of the public. They are quick and easy to deploy making them singlehandedly one of the greatest survival tools to have on hand. No one ever hopes to have to use an emergency flare, however having one and knowing how to safely use it will keep you out of harm’s way when unexpected times transpire.