Arrived on site, client said they had no hot water, tried lighting pilot and would not light. Unit is from 2010. Gave diagnostic options to client. After diagnostic, was able to light pilot and water fired up with no issues, waited approximately 20 minutes and everything still working properly. Not very much combustible air in mechanical room, recommended leaving door open, or creating slats in door to allow more airflow. Left estimates with client for replacement. If issues continue, recommend replacing unit based on age as well.