De or het vochtletsel?

The correct Dutch article is:

het vochtletsel

Rule Words ending in -sel: usually het. See the rule

How to use vochtletsel

the vochtletselhet vochtletsel
this vochtletseldit vochtletsel
that vochtletseldat vochtletsel
our vochtletselons vochtletsel
your vochtletseljouw vochtletsel
every vochtletselelk vochtletsel
which vochtletsel?welk vochtletsel?
a big vochtletsel / the big vochtletseleen groot vochtletsel, het grote vochtletsel