Truth be told on why the haz mat surcharge. Not every carrier is allowed to carry haz mat. You must be haz mat certified. Usually, carriers will charge you a haz mat fee for every UN number. This number is dictated by the class of haz mat. for Example, Explosives is Class 1 haz mat. Class 2 is compressed gas, class 3 is flammable liquid, class 4 is flammable solid.... so on and so forth. you have radiactive, oxidizers, poisonous, corrosive, even magnetic can be hazardous in air craft.
This freight must be packaged and labeled correctly and the correct documents must accompany the Truck bill of lading, Ocean bill of lading or if your shipping via air, Air way bill. The truck trailer or container must also be dressed with the correct haz mat placards. There must be a hazardous material declaration which includes, the Class, Un number, Flash point, and 24 hour contact as well as the shipper and consignee info, pc count weight and dims. Since not every carrier or freight agent is DGR Certified (Dangerous Goods/Restricted articles), they can and will charge a Haz mat fee/surcharge. $20.00 is not that bad. Aircraft cargo is it usually around $75.00 - $95.00 per UN number. Heaven forbid you ever want to ship this stuff out of the country because then you will need to have the U.S. State Dept issue you a DSP-73 license / permit. You will need to be licensed yourself and be able to make compliance or believe me, U.S. Customs can and will be a pain when it comes to this. Probably even cease your freight.
LGB