building building construction chinese Chinese architecture confined confined space construction construction site flame flare heat helmeted helmets safety safety harness welder welding work worker working workmen access-limited advice advising alert appropriate-behavior appropriate-behaviour authorised-entry-only authorized-entry-only behave behavior behaviour black care caution communicate communication concern confined-space danger dangerous information informing lettering limited-access limited-permission limited-space red restricted restriction restrictions risk risks risky sign signage unauthorised unauthorized warning warning-sign white