When you’re thinking of purchasing a flashlight, you’re probably looking for a simple handheld device that can make a dark area visibly brighter. However, flashlights come in many different forms, for just about every part of the light spectrum. In addition to lights that shine in different colors like red or ultraviolet lights for finding stains, there are also infrared (IR) lights that shine in a light completely imperceptible to human eyes. On its own, such a device wouldn’t be especially helpful, but when paired with a pair of night vision goggles, an IR flashlight can suddenly become quite invaluable.

IR light is typically used as a means of connecting devices wirelessly, like the IR beam fired from your remote to your TV to send it signals. Because its wavelengths are longer than what human eyes can perceive on the visible spectrum, it can’t provide light on its own. This is why, rather than a “flashlight,” it may be more accurate to refer to an IR iteration of such a device as an “illuminator.” Rather than just shining a beam that you can see on its own, an IR flashlight “paints” your surroundings in IR light, which can then be picked up by light-sensitive equipment like night vision goggles.

The human eye is capable of perceiving light in the electromagnetic spectrum ranging from roughly 380 to 700 nanometers. This allows us to see, for example, the bright yellow light of the sun, as well as lights shining in cooler colors like green, blue, violet, and so on. However, infrared light’s band on the electromagnetic spectrum measures between 780 nanometers and 1 millimeter, which means a human eye can’t see it, at least on its own.

This is where equipment like night vision goggles come in. Night vision goggles can pick up a much wider band of light from the electromagnetic spectrum, including infrared light. Whatever light it picks up is then amplified a thousand-fold, brightening and sharpening it to a point that you can see it. However, the catch here is that infrared light needs to actually be present for night vision goggles to pick it up. If you’re in a spot where there’s not even trace amounts of light from the stars or a distant city, even night vision goggles will leave you in the dark. It’s in these specific situations that an IR flashlight becomes your secret weapon.

Rather than merely creating a beam of light for the purposes of illumination, an IR flashlight instead covers the surfaces it shines on with infrared light particles. By painting your surroundings with infrared light. Even if you can’t see it with your naked eye, you create circumstances where a pair of night vision goggles can properly see things again.

An IR flashlight is a vital tool for various circumstances and professions. For example, search and rescue personnel can use them in caves or under dense forest canopies to search for missing people in a more efficient manner than a regular flashlight could provide. Law enforcement officers and SWAT teams can use them in nighttime sting operations, waving IR flashlights around to see figures in the dark with night vision without alerting anyone to their presence. It could even be used to help navigate out on the open ocean waters during a dense cloud cover over the moon. A combination of an IR flashlight and a night vision lens is also helpful for hunting or wildlife photography, as it allows you to see critters in the dead of night without scaring them off.