signs biosafety levels. bsl-1 2 3 4. laboratory biohazard warning . from low to high risk of infection. ecology and

biosafety level biohazard symbol infection biological science icon dangerous weapon bio laboratory safety danger bsl sign set vector scientific warfare virus agriculture chemistry exobiology synthetic healthcare risk group information ecology international medicine warning medical waste management occupational pollution protect contamination attention low high microbe caution bacteria environment epidemic signs levels bsl-1 symbol infection isolated white background