Well this is a fun topic, innit?
Inklings and Octolings, if they aren't completely destroyed, always become a Spirit while they are 'in-transit' to a Respawn Point. If they spend too long (upwards of a minute) as a Spirit in open air, they will begin to disintegrate until they are truly dead.
Put simply, being prevented from reaching a respawn point can cause death.
This could be from obstructing the path to a respawn point...
Or from being too far from a respawn point without an Anchor (Respawn Points are very rare outside of Inkopolis City)...
Another tool engineered by Octarians for use against Inkling victims is the Disruptor, a subsonic emitter that vibrates the entirety of one's person. When affected, the victim cannot become a squid (or octopus), as their cells cannot settle long enough to initiate the change. This also means that a Spirit simply cannot form if the victim is splatted, causing an instant death.
Keeping one’s spirit isolated from the open air will keep the spirit from disintegrating.
The most common method for doing this is with some sort of containment device - even a sufficiently sized household jar will usually suffice if it is available.
Anchors are devices attached to one's person, 'binding' them to a Respawn Point. Whereas normally a Spirit would be drawn to the nearest Respawn Point, if any, a Spirit with an Anchor will always be pulled toward its anchoring Respawn Point.
Anchors come in two forms: