Our office is small open plan office which is 90sqM with another similar office above on first floor. Ground floor is rented by us and the first floor is another separate business.  Do we need a fire alarm system or would domestic interlinked smoke alarms suffice? 

Domestic smoke alarms are just that, for use in domestic premises, not commercial. What does the fire risk assessment say?

On 24/10/2023 at 05:55, Guest Mark said:

Our office is small open plan office which is 90sqM with another similar office above on first floor. Ground floor is rented by us and the first floor is another separate business.  Do we need a fire alarm system or would domestic interlinked smoke alarms suffice? 

In premises of more than one storey, an electrical fire alarm system should be installed. These systems should have ‘break glass’ call points and fire alarm sounders,  connected to a control panel. (Not domestic smokes!)

In premises of more than one storey, where a fire might start and be undetected in its early stages, the fire alarm system might need to incorporate automatic fire detectors. These will generally be smoke detectors or, in the case of kitchens or other rooms in which smoke detectors would cause false alarms, heat detectors).

As per https://www.gov.uk/government/publications/making-your-small-non-domestic-premises-safe-from-fire This guide has Article 50 status meaning following it will ensure you are deemed compliant, not following it tends to demonstrate non compliance with the legislation.