When dealing with heating ventilation and air conditioning, the unit that handles it needs to be properly protected, with a good HVAC hinge units and sealing to ensure that it wont get damaged or sabotaged by outside forces. This isn't limited to just human error and involvement either, temperature, weather and the overall climate all needs to be taken into consideration when designing the access and protection of a HVAC unit. If it isn't all properly sealed, there's a noticeable increase in risk of both damage and reduction of the lifespan of the unit since water can and will eventually corrode metals. There's little point in trying to be cheap since the damage and safety issues is not worth saving a few bucks, so it's always better to get proper items like a sturdy HVAC hinge or latch to help make sure that it's all properly sealed.
Designing access solutions
While designing the access solution for the unit responsible for the heating and ventilation, you need to make sure that the conditions it will be under, what weather and temperatures that it will have to endure so that there's less risk of corrosion and damage being made on the exterior. There'll also be a need for depressurizing the unit and for there to be a way out of the door somehow shuts as well as durable HVAC hinges to make sure that the door can be opened properly without any risk of sudden problems arising while you're inside.