---
title: "Environment and stops"
description: "The Environment section and the Stop Settings card: water type, altitude, the stop grid the schedule is rounded to, and the two ppO₂ ceilings."
---

> Documentation Index
> Fetch the complete documentation index at: https://docs.divelogic.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Environment and stops

import { EnvironmentCard } from "@/components/react/PlannerSettingsScreens";

Water type and altitude change what a metre of depth is worth. Three further
settings change the shape of the stop list the schedule is rounded onto.

## Water type and altitude

The **Environment** section holds exactly two fields.

- **Water Type**: **Salt Water** or **Fresh Water**, at 1025 kg/m³ and
  1000 kg/m³, which works out at 0.1005 bar per metre in salt and 0.0981 bar
  per metre in fresh.
- **Altitude (m)**: metres above sea level. It sets the surface pressure the
  whole dive is referenced to: 1.01325 bar at sea level, about 0.894 bar at
  1000 m, about 0.789 bar at 2000 m.

Both feed one quantity, absolute pressure at depth, so their effects compound.

> **Caution**
>
> Altitude also changes the pressure the diver *surfaces to*, which is what
> governs the shallow stops. Leaving it at 0 makes the model believe the diver
> surfaces to a full atmosphere they will not find.

## The stop grid

Three settings decide where stops may be placed and how short one may be. They
live in the **Decompression** section, in the **Stop Settings** card.

- **Min Stop Time**: 10 seconds, 30 seconds or 1 minute, starting at 1 minute.
  At 1 minute, a stop the model would clear in twenty seconds is still written
  as a full minute.
- **Stop Increment**: 1 m through 6 m, starting at 3 m. The spacing of the grid
  stops are rounded to. At 3 m they fall at 3, 6, 9, 12 m; at 1 m the planner
  can hold you at any whole metre, for a longer stop list and a slightly
  shorter total.
- **Last Stop Depth**: 3.0 m through 9.0 m in 0.5 m steps, starting at 6 m. The
  shallowest stop the planner will schedule; from there the diver ascends
  directly to the surface at the *Last Stop → Surface* rate. A 6 m last stop
  moves decompression time deeper, which costs runtime.

## The two ppO₂ ceilings

Every gas is judged at every depth against two oxygen partial-pressure limits,
neither editable per dive.

- **The bottom limit, 1.4 bar**, applied at each level's depth. Exceeding it
  produces a **Warning** naming the gas, the depth and the ppO₂ reached; the
  schedule still computes.
- **The decompression limit, 1.6 bar**, the absolute ceiling. Any point in the
  plan where ppO₂ exceeds it produces an **Error**.

The per-gas ppO₂ limit set on each mix is editable, and the planner uses the
stricter of the two. These are availability rules, not exposure accounting:
cumulative exposure is tracked as CNS % and OTU on the Review step.

## Next

[ICD safety](/planning/icd-safety) is the last section of the Plan step: what
the planner should object to when you change what you are breathing.

Source: https://docs.divelogic.ai/planning/environment/index.mdx