The cartridge can be checked by unscrewing the safety cap and checking the little sealing disc. If the cartridge has been pierced it will be easily visible. However, the possibility that the cartridge may not have a proper seal cannot be disregarded. The cartridge is under immense pressure. A hairline fracture, a defect seal or thread could cause a leak or loss in pressure and therefore the apparatus would malfunction It is therefore a must to always check the cartridge before use. This is only possible by comparing the weight. Each cartridge shows the weight on the cap. By re-weighing it can be checked quite easily. Should the weight differ by more than 5g, the cartridge should not be used. The company will issue a replacement free of charge. With the trigger handle of the dual system the pin, which attaches to the pressurized hose must be affixed tightly. This can be checked by pulling slightly with your fingers. Most importantly a red band on the pin should not be visible as it is an indicator that the handle has already been activated. Attention! Do not under any circumstances pull out the pin with pliers or your teeth. This could have serious consequences.