Get the word out on your Dangerous Good shipments with Labelmaster's Dangerous When Wet Worded Placards. Available in a variety of materials, these Hazard Class 4 placards meet the requirements of 49 CFR 172.500 for domestic and international shipments of hazardous materials by highway, rail and water. Keep your focus on the task at hand. We've already done all the testing to ensure these placards meet the standards set by the DOT and other regulations, so your shipments will arrive on time and fully compliant.