In general it is not a good idea to open your incubator during hatching. It lets out both heat and moisture, and can cause later hatching chick to not hatch properly. Chicks that have difficulty hatching on their own are more likely to have other problems as well. If you do HAVE to open your incubator, take it into a hot, steamy bathroom and open and close it quickly.
You might find these articles from the Learning Center helpful -
Hatching 101 - https://www.backyardchickens.com/a/hatching-eggs-101
Assisted hatching - https://www.backyardchickens.com/a/step-by-step-guide-to-assisted-hatching
You might find these articles from the Learning Center helpful -
Hatching 101 - https://www.backyardchickens.com/a/hatching-eggs-101
Assisted hatching - https://www.backyardchickens.com/a/step-by-step-guide-to-assisted-hatching
