Hi Matt, Thanks for your response! If I do h5ls -r on a particle file that has no particles, I get: (base) RSAA-043527:Documents psharda$ h5ls -r FLASH_part_0003 / Group /integer\ runtime\ parameters Dataset {136} /integer\ scalars Dataset {17} /localnp Dataset {585} /logical\ runtime\ parameters Dataset {147} /logical\ scalars Dataset {2} /real\ runtime\ parameters Dataset {206} /real\ scalars Dataset {13} /sim\ info Dataset {1} /string\ runtime\ parameters Dataset {152} /string\ scalars Dataset {1} /unknown\ names Dataset {37, 1} If I do the same on a particle file that has particles: (base) RSAA-043527:Documents psharda$ h5ls -r FLASH_part_0044 / Group /integer\ runtime\ parameters Dataset {136} /integer\ scalars Dataset {17} /localnp Dataset {2753} /logical\ runtime\ parameters Dataset {147} /logical\ scalars Dataset {2} /particle\ names Dataset {37, 1} /real\ runtime\ parameters Dataset {206} /real\ scalars Dataset {13} /sim\ info Dataset {1} /string\ runtime\ parameters Dataset {152} /string\ scalars Dataset {1} /tracer\ particles Dataset {3, 37} /unknown\ names Dataset {37, 1}