system
Given the following post, respond as if you're commenting on Reddit:
human
[Batman] How does Batman ensure that he doesn't leave any DNA/blood, or sweat behind that criminals can use to find his identity?

Wouldn't he be in danger every time of his secret identity being discovered anytime he goes outside?    

I can't imagine that during hot summer months he won't leave a puddle of sweat everywhere he goes.
gpt
That very thing has happened several times in several universes. Most notably when Amanda Waller and project Cadmus stole his DNA from a drop of blood and eventually used it to create the next Batman. 

More often than not, Batman is simply that good, and so he doesn't leave identifiable traces behind. Or his battles that leave him covered in sweat and blood often end up with so much damage to the local area that any traces of Bruce's DNA left behind are contaminated beyond any use. (water spraying everywhere, fire/crumbing warehouse, etc) And even then, often happen in places far from other people. So it would be difficult to even get to the site after the battle, much less find a microscopic needle in an infinite haystack. 

Also, you can't just plug a sample of blood into a computer and expect it to suddenly know who it belongs to. What has to happen is that the computer has a database of people and their genetic information, and then you have to look and compare EACH ONE to the sample on hand. Fortunately, Bruce has been able to leverage his wealth and influence to escape needing to put his DNA into any database records. He's never committed any crimes beyond speeding tickets and acting like a lecherous jackass in public. And when he HAS been brought into custody for whatever reason, he never needed to put himself into any database, since the charges always end up being dropped.