If an employee doesn't show up to work, how long is typical before the company i...

(Not sure if this is on-topic)

This is hypothetical and is for the plot of a story I'm thinking about.

If an employee doesn't show up for work, how long is typical before the company investigates? For example if the employee suffers a fall that disables them, how long will it take before they can expect their workplace to summon an ambulance?

I'm only looking for an order of magnitude estimate: hours? One day? Two days? A week? A description of the typical protocol if this happens will also be helpful.

Tagging this with human resources because I imagine if anyone at the workplace investigates, it's HR.

1. Companies will in general not call emergency service unless there a strong indicators (with supporting hard data) that something is really off. This would be rare.
2. Manager or HR will first try to contact the employee by phone or message.
3. If there is no reply after more than a day, they might try to contact the emergency contact of the employee. Once the emergency contact has been notified, any further action is up to them, not the company. If the employee has not given an emergency contact, that's typically a sign that they don't want the company in their personal business, so the company has no responsibility to follow up.
4. A concerned employer may encourage some other employees that could be considered "friends" or "good personal relationship" to reach out. But this is pretty much all they can do.
5. Many companies have an "abandonment" clause. Example "if you don't show up 3 days in a row without notification, we assume that you have abandoned the job". This legally terminates the employment.