Since each student's accommodation needs are unique and the student is often most knowledgeable about effective accommodations, be sure to talk with the student about what accommodations he/she might need.
Some specific accommodations that might be useful to a student with a health impairment in a science lab include the following:
- Avoid chemical materials to which the student is allergic or provide an alternate assignment.
- Allow for a flexible schedule and time allocation.
- Provide detailed instructions.
This list is from the DO-IT publication Making Science Labs Accessible to Students with Disabilities .
For more examples of accommodations that can be made in science labs consult the DO-IT Knowledge Base article What are examples of accommodations in science laboratories? 
-  Making Science Labs Accessible to Students with Disabilities
-  What are examples of accommodations in science laboratories?