Robyn.
Standards NZS 5235.1:1978 and 5235.2:1978 were the Codes of Practice for Safety in Mechanical Refrigeration (the Refrigeration Codes). 5235 Pt 1 refers to refrigeration systems with a total refrigeration effect or input energy in excess of 30 kW. 5235 Pt 2 refers to plant with input of less than 30 kW. 30 kW + is typically large freezer units found in freezing works, large cold storage facilities and food processing plants with large or multiple blast / storage freezers. Less than 30 kW plants are typically those walk-in freezers found in small commercial businesses such as butcher shops, food retailers, hotels, restaurants, and small transit depots for frozen goods.

I have a copy of the NZS 5235:1 -1978 version but not 5235:2. These two standards were updated in 1988, and then superseded by AS/NZS 1677 Pts1 & 2 in 1998.
As technology has changed so has the content of the standards. There is a greater focus on the range of hazards presented by the type of refrigerant used in the later standards. I suspect this has been refined yet again following the Tamahere cool store fire in the Waikato. You can purchase the standards for around $60 each.

In regard to your question about access/egress the principles are largely unchanged from the original Codes. There are requirements for both the plant room which houses the refrigeration equipment (refrigerant storage, compressor system) and the cold room (freezer) where product is stored. A cold room/freezer is defined as one where the operating temperature is at 5°C or below. The number of egress doors is determined by the size of the freezer space. There are requirements for illuminated exits, minimum door size, doors able to be opened outwards without use of a key, emergency signalling devices etc etc.

In the interests of providing general information but keeping my reply reasonably short, I can scan and email you a copy of the safety checklist for the codes if you wish. These are still relevant and completed checklists would be evidence that reasonably practicable steps have been taken to ensure safety in relation to refrigeration plant.

The 1998 standard has been superseded by AS/NZS 5149:2016 Pts 1-4