Hi there, a First Time Mum here, I am looking at using the Bloom Alma Mini Crib as the first sleeping space for my baby, however the mattress I've found to be most suitable (the Save Our Sleep mattress specifically designed to fit this crib and purportedly meeting voluntary standard AS/NZS standard 8811.1:2013) is more than 75mm thick, being 120mm thick. Can you please explain why mattresses should be no more than 75mm thick to avoid suffocation? Many thanks!

Red Nose recommendations for a cot mattress, are that the mattress be firm, clean, well-fitting & flat (not elevated)
https://rednose.org.au/article/what-is-a-safe-mattress
If the company says that it meets the voluntary standard for firmness, then it should be fine.

Does this crib comply with mandatory cot standards or does it come under guidelines for bassinets?
https://rednose.org.au/article/what-is-a-safe-cot
Product Safety Australia (ACCC) develop safety standards in Australia.
There are no mandatory standards for bassinets in Australia, however, they provide the following information (as Buying Tips) for bassinets.
These are not mandatory; they are safety recommendations.

Ensure the sides of the bassinette are at least 300 mm higher than the top of the mattress base.
Ensure it has a wide stable base and a sturdy bottom so that it won’t tip over.
Ensure the mattress fits well and is firm, smooth and no more than 75 mm thick.
If the product has folding legs, make sure it cannot accidentally fold during use.
https://www.productsafety.gov.au/products/babies-kids/kids-furniture/bassinettes

The thickness of the mattress in a bassinet is generally related to the firmness as well as ensuring there is sufficient height of the sides of the bassinet (eg 300mm - as above)
A soft mattress in a cot or bassinet is not recommended, as it may pose a suffocation risk.

The Bloom Alma Mini complies with Australian cot standards. Contact the Australian supplier of the Bloom products and they can provide the details for the AS