All resin and gel coat containers with a capacity equal to or greater than 208 liters (55.0 gallons), including those used for on-site mixing of putties and polyester resin putties, shall have a cover with no visible gaps in place at all times. This work practice does not apply when materials are being manually added to or removed from a container, or when mixing equipment is being placed or removed from a container.
06- 096 C.M.R. ch. 162, § 7