The Nu-Calgon 4182-24 Cal-Blue Plus Micro Gas Leak Detector has outstanding freeze-protection down to 5°F (and up to 225°F). Cal-Blue products are the complete gas leak detector. Not only do they detect the smallest leak, they also provide other significant benefits. The high viscosity formula provides long lasting bubbles, and enables the product to remain in contact with the applied surface for an extended period of time, thereby allowing the smallest of leaks to be detected. It is also non-corrosive to metal, and this is a significant feature as it helps to maintain the integrity of piping, tubing and fittings. THE NU-CALGON 4182-24 CAL-BLUE PLUS MICRO GAS LEAK DETECTOR IS FOR PROFESSIONAL USE AND SHOULD ONLY BE USED IN ACCORDANCE WITH ALL REGULATIONS AND PROPER SERVICE PRACTICES. PLEASE SEE PRODUCT LABEL OR CONTACT NU-CALGON DIRECTLY FOR USE INSTRUCTION. IT IS RECOMMENDED TO UTILIZE THE APPROPRIETE PPE (PERSONAL PROTECTIVE EQUIPMENT) DURING APPLICATION.