  Context: Optically luminous quasars are metal rich across all redshifts.
Surprisingly, there is no significant trend in the broad-line region (BLR)
metallicity with different star formation rates (SFR) and the average N V/ C IV
metallicity does not appear to exceed $9.5~Z_\odot$. Combined, these
observations may suggest a metallicity ceiling.
  Aims: Here, we conduct an exploratory study on scenarios relating to the
evolution of embedded stars that may lead to a metallicity ceiling in quasar
disks.
  Methods: We develop a simple model that starts with gas in a ''closed box'',
which is enriched by cycles of stellar evolution until eventually newly formed
stars may undergo significant mass loss before they reach the supernovae stage
and further enrichment is halted. Using the MESA code, we create a grid over a
parameter space of masses ($>8~M_\odot$) and metallicities ($1-10~Z_\odot$),
and locate portions of the parameter space where mass loss via winds occurs on
a timescale shorter than the lifetime of the stars.
  Results: We find that for reasonable assumptions about stellar winds,
sufficiently massive ($8-22~M_\odot$) and metal-rich ($\sim9~Z_\odot$) stars
lose significant mass via winds and may no longer evolve to the supernovae
stage, thereby failing to enrich and increase the metallicity of their
surroundings. This suggests that a metallicity ceiling is the final state of a
closed-box system of gas and stars.
