Why use a specialised provider for smoke alarm compliance ?

You could install and maintain smoke alarms yourself and ensure you disclose this to your insurance company. If you are prepared to visit the property at all lease changes and can address faulty smoke alarms quickly, maybe you could but then you might struggle to provide the signed off, photographic evidential trail that a professional can supply.
It makes a lot of sense that property managers don’t want to carry decibel meters, ladders and drills as it is not part of their job description and real estate agency ACC & Work Safe may be affected. It would be difficult for them to cart the tools of trade and safety equipment around with them such as ladders decibel meters volt meters drill and tool bag, especially for the female property managers, often in female attire!

The other reasons why property managers shouldn’t do this job is that they are not trained extensively to conduct this type of work and we question if any agents are disclosing this practice with ACC, Work Safe, professional indemnity and public liability insurers. I doubt any agent wants to be the first test case.
A professional does a professional job, there are no halves. Using professionals is an investment in having it done right and the right professionals like HHAST have the relevant insurances to cover their work, conduct and professionality.
All properties are automatically re-enrolled and invoiced annually unless otherwise notified to ensure your property remains compliant year in and year out.