Paint fumes were clearly visible in the building, WorkSafe chief inspector Karen Davidson said.
Poor hazardous material management was a significant contributor to the estimated 600 to 900 New Zealanders who die every year from work-related ill heath, she said.
"Many workers suffer ill health and premature death from workplace exposure to chemicals and isocyanate-based paints like those used by L&L Marriott Holdings Limited," she said.
WorkSafe issued a prohibition notice, forbidding all spray painting until a compliant spray booth was installed.
But the company breached the notice three times throughout 2014, putting employees at "significant risk", Ms Davidson said.
"Prohibition notices are there for a reason - to keep workers safe."
The Dangers:
•Solvent vapours are particularly dangerous for people who work with them regularly.
•Breathing in solvent vapour fumes can result in long-term effects such as memory loss, fertility problems, loss of concentration and moodiness. Short-term effects include headaches, dizziness and nausea.
•Isocyanates, found in spray paint, can lead to chronic asthma and respiratory problems.