You must have DANGER SIGN and ORANGE BLOCK to make BIOHAZARD SIGN. Category: building. Plant and harvest in one session. Received experience is a mystery. Keep an eye out for the exp counter. BIOHAZARD SIGN can be broken. Seed mathematics is very complicated, but you should get at least 1 seed back from splicing BIOHAZARD SIGN. Will you strike it rich? You just have to count the gems yourself. Blockratio of BIOHAZARD SIGN is a mystery. Maybe you can check the wiki for <a href="https://growtopia.fandom.com/wiki/Biohazard_Sign">biohazard sign</a>