Where an emergency shower can go is decided by plumbing before it is decided by distance. A shower needs a water supply and, much more awkwardly, somewhere for a few hundred litres to go. An eyewash needs the same on a smaller scale. Neither is a piece of furniture that can be slid to wherever a reach calculation would prefer it.
Services first, and as a hard error
The service rule in LabPlanner is an error, not advice: a unit needing piped services must back onto a wall that provides all of them, and showers, eyewash units and combination stations need water AND drainage together. Water alone is not enough. A shower plumbed onto a wall with no drainage is a flood in the one situation where nobody is going to stop and think about the floor.
This is checked rather than preferred. The placement engine reports that a shower cannot be placed instead of putting one on a dry wall, and what it reads are the per-wall service flags entered during room setup. Those flags are the most consequential thing typed into the app, and the most frequently guessed at.
Nearest the exit, on the wet wall
Given a choice of walls that can serve it, the engine seats the body shower on the wet wall nearest the door. That preference came out of the reference drawings rather than out of a clause: five of the ten projects reviewed place the body shower at the entrance, beside the exit.
It is a sensible instinct. The person who needs it is on their way out, or has just come in, and the door is the one location in a room that everybody can find without looking for it.
The 900 mm side clearance is a preference
Safety units are packed with 900 mm of clear space either side wherever a wall run offers it. This is a packing heuristic and not a checked rule, and the distinction was learned the hard way. Treated as a gate, it produced layouts with no eyewash station at all in rooms whose wet walls were short — the rule rejected every candidate position and the unit was quietly dropped.
A room with a slightly tight shower is safer than a room with no shower. So if no run offers the clearance, the unit is placed without it and the constraint is recorded rather than enforced. This is the general shape of the honest answer whenever a safety heuristic and a real room disagree: place, disclose, and let a human decide.
Being found matters as much as being near
Two checks guard visibility rather than distance. Tall and overhead cabinets keep 900 mm from doorways and must not hide a safety unit from the sightline of the door, which is reported as a warning; and the doorway approach itself stays clear of everything. A shower standing behind a tall cabinet is a shower nobody locates with their eyes shut.
The industrial drawings also show an idiom worth copying: eyewash integrated into task sinks, rather than concentrated at a station by the door. It puts the water where the splash happens. Model it by placing an eyewash unit at a sink position — the checker treats it the same way, and the schedule prints it as its own line.
The rule that was removed
Version 0.6.0 of the rule set removed a travel-distance check modelled on the familiar ten-second reach principle. Describing that removal is probably the most useful thing this note can do, because the check looked authoritative and measured the wrong thing.
The app has no pathfinding. It could measure a straight line from a work position to the nearest shower, and a straight line is not a route: it runs through bench runs, island ends and fume cupboards as though they were not there. A layout with a shower eleven metres away round two islands would have satisfied a ten-second test that a person with their eyes shut could not. A number that resembles a code check without performing one is worse than no number, because it invites reliance. Loaders strip the rule out of older saved configurations rather than silently re-checking against it.
What remains is stated as an approximation and labelled as one. Escape continuity is approached through aisle widths, door swings and cabinet egress buffers together, and it is not presented as verified routing. The gap between those two statements is exactly the gap a designer has to close by walking the room.
What still has to be checked by hand
- The actual route from every work position to the unit — walked, not measured across a diagram.
- Water temperature, supply flow rate and duration, which are equipment and services questions rather than layout ones.
- Commissioning, periodic testing, signage and permanently unobstructed access, all of which are operational and outside any layout model.
The geometry on a drawing is the beginning of this argument, not the end of it.