You get the UV Flashlight in Dying Light 2 Stay Human on the PK Floating Fortress during the Welcome On Board mission. Meyer gives it to you shortly after you meet Major Jack Matt for the first time. She tells you it’s useful, but not exactly how to use it. You probably thought at first that this was going to be a powerful upgrade to your existing flashlight, but by now you will have discovered that this is not the case. In fact, the UV Flashlight occupies a completely different place in your inventory to the regular flashlight, and is operated using totally separate controls.
The UV Flashlight is an accessory, like throwing knives, decoys and molotov cocktails, so to use it, you have to equip it first. Go to your inventory tab and select the accessories section. Select the UV Flashlight as one of your four equipped accessories, then equip it.
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Now go somewhere dark, find some Infected, and provoke them into attacking you. With the UV Flashlight equipped, press and hold LR/LT/MMB to switch off your regular flashlight and use the UV Flashlight instead. Infected caught in the beam will stop and cower, making them vulnerable to attack, but the effect won’t last long, as the battery life is limited and will need to time to recharge. The UV Flashlight isn’t very effective when you first get it, but it can be upgraded by a Craftmaster in exchange for Military Tech.
