First, the discussion about epoxy
vs ester can be well informed by watching several Youtube videos by "Boatworks Today" showing advantages to both project
dependent. He also has a pretty good discussion about shop ventilation and a novel ventilation system for cold weather
Second, notwithstanding the interesting seat of the pants discussion about Epoxy
hazards and the personal experiences and opinions I can add a couple things from a professional standpoint as an Industrial Hygienist of almost 40 years experience in heavy, medium and light industry. The issue of lighter or heavier than air is a completely irrelevant question in anything but a completely still closed box, which is important for propane
or gasoline on a boat
, but not in a fabrication shop of any kind.
The Epoxy part A itself is pretty benign, while the Hardner depending on the formulation is a very potent sensitizer with a wide variability of sensitivity amongst the population. Some folks working day after day never show sensitivity, and others become intolerant very quickly. Regardless you do not want to become sensitized. Variations in the products comes from how much free amine evolutes from the hardener which, in turn, is determined by the volatility and polymerization of the amine itself. MFG have, as noted, become very much better at producing a usable product with a minimum of outgassing of the free amine. However, free amine has to be there in order for the epoxy to polymerize and harden so NO epoxy is free from this hazard regardless of MFG claims.
Skin exposure is as or more an issue than inhalation and very strict measure need to be taken to minimize this by PPE including frequent changes of gloves and even suits because the amine will penetrate gloves and suits if it sits on the surface of the PPE. A good organic vapor respirator with frequent cartridge changes is sufficient for all but the highest volume projects, but supplied air or Powered air purifying units (PAPR) are even better.
Ventilation is ALL about getting strong airflow (eg. not the little air fresheners or whatever) and LOTs of activated carbon if not pumped out of the building and replaced with fresh air. A downflow booth like a spray paint
system is optimal as it draws the vapors (not fumes) away from the breathing zone of the worker, and makeup air pulled from above. This is not practical for home operations but can be approximated by pulling air from below and close to the area of application and introducing makeup air from the ceiling.
Hope this helps a bit.