Greetings brother! Your post is really informative and educational. You have explained the biosafety levels from BSL-1 to BSL-4 very well with clarity. BSL-1 includes low-risk bacteria like non-harmful E. coli that can be worked on on an open table. BSL-2 includes viruses like hepatitis and staphylococci that can cause human diseases. BSL-3 describe serious diseases like TB and yellow fever in this HEPA filters and one-way air systems are compulsory. BSL-4 has the most stringent safety measures for deadly viruses. Thanks for sharing informative post.