In the Netherlands, if you have employees who work in enclosed spaces (cellars, cooling cells, sea containers), you must protect them against suffocation, intoxication, poisoning or fire (in Dutch). If you suspect a hazardous situation in such a space, you must hire a gas expert to measure whether hazardous substances or toxic gases are present. Employees may only access the space after measurements have shown that there is no danger.
In the construction sector you must have a Health and Safety Plan (Veiligheids- en gezondheidsplan, V&G-plan) in place for work in enclosed spaces. You must put measures to prevent certain dangers in the company emergency response plan. Also, a superior must inform and instruct employees about dangers, measures and procedures.