From a health perspective (and depending how cold the chiller is) consider a medical questionnaire to ensure person who are required to work in the cold conditions do not have any existing medical conditions that could be made worse by the cold (and a requirement for them to inform management of the onset of any symptoms). Not sure how big the container is (I assume smallish if you're referring to it as a container not a chamber) but if you've got powered MHE working in there, make sure the batterys are suitable for cold environments.

Have a look at the thread "Working in Freezers" started in mid-March this year. I've just added a response to it, partly to bring it back from semi-oblivion to forum page 1 for convenience. On a wider scale, during my HSE years I visited a number of factories which processed and packed fruit and vegetables. In order to prevent premature spoilage of the products the workrooms had air-conditioning which kept them cold. In view of this, various measures were used to try to prevent employees from becoming cold, e.g. thermal clothing, job rotation & work breaks and localised radiant heating. Also, one of my HSE colleagues investigated a fruit factory after receiving reports of serious frost bite in a number of temporary seasonal employees. It transpired, I think, that the temperature setting of one or more machines for freezing the fruit had been deliberately set too low, presumably in order to speed up the throughput. However, the employees who had to handle the abnormally chilled fruit weren't adequately protected by their gloves which would have been effective under normal conditions. This led to a prosecution report which included relevant industry codes of practice plus statements from the injured employees and also relevant medical and industry experts. Faced with this, the employer pleaded guilty and was fined.