Blend Planner | Dive Kit

What it is

The Blend Planner tells you how to physically fill a cylinder to a target mix. You give it what is in the cylinder now, the mix and pressure you want, and the gas you have to blend from. It hands back the steps in order: how much to bleed off, what to add from which bank, and to what pressure. In the app this screen is titled Blend Planner.

It is the reverse of the Mix Result tool. Mix Result tells you what mix you get when you top up a cylinder; Blend Planner works backwards from the mix you want and tells you how to get there.

The planner runs in two modes you switch between at the top: Partial (partial-pressure blending, the default) and Continuous (continuous-flow blending for a mixing panel).

Partial-pressure blending

This is the standard method: you add each gas in turn and watch the pressure climb, because at a fixed temperature each gas adds pressure in proportion to how much of it you put in.

On first open the screen comes pre-loaded with an example: a Trimix 18/45 target from 150 bar of leftover EAN32 in an 11 L cylinder, so you see a real multi-step plan straight away. Edit the Current and Target values to match your own fill.

Set up the cylinder

In the Cylinder card, set the Current state: the cylinder volume, its current pressure, and what is already in it (O₂% and He%). Then set the Target state: the O₂%, He%, and pressure you want to end at. An arrow between the two shows the transformation. The He% field is always shown in both states; leave it at 0 for a nitrox fill. Tap Quick Fill to pull a saved cylinder profile, which sets the cylinder size and pre-fills the target gas and working pressure in one tap.

Tell it what you can blend from

In the Banks card, manage your gas sources. Air, pure O₂, and pure He are there by default as unlimited banks (the app calls these Unlimited: a shop supply that never runs out). Add a limited bank (the app calls these Limited) for a portable bottle by giving it a pressure and volume, so the planner can respect how much gas it actually holds. Each bank carries an O₂% and an He%.

Set the environment if it matters

Open the Environment section to set altitude, ambient temperature, and fill temperature. These adjust atmospheric pressure and the hot-fill correction. Sea-level defaults are fine for most fills.

Read the plan

The Plan lists the steps in order. When more than one valid plan exists, a toggle lets you compare them, ranked by accuracy first and fewest steps second.

Save the cylinder (optional)

The Cylinder Bar lets you save and reload cylinder setups by name, so a cylinder you blend often is one tap away. Banks and environment are shared across all your saved cylinders.

What the steps mean

Step	What you do
Bleed	Drain the cylinder down to a stated pressure before adding gas. Needed when the current mix is too rich, or to make room for the right blend
Add Bank	Fill from a named bank up to a stated pressure. The step shows the resulting O₂% and He% once it is in
Settle (shown as Cool down / Warm up)	If you filled warm, this shows how the pressure will drop as the gas cools to ambient, so you fill to the right final pressure

The result panel names the mix the plan actually reaches and its final pressure. Because real banks do not hit a fraction exactly, the planner ranks alternative plans by how close they land to your target. If no valid plan exists (the target is impossible from the banks you have), it explains why and shows the closest partial plan it could build.

Continuous blending

Continuous mode is for shops with a mixing panel that blends gas as it flows into the cylinder, rather than adding it in pressure steps. Switch to the Continuous tab.

The panel feeds are fixed: Air, O₂, and He are metered into the air intake, so there is nothing to configure. You only set the cylinder’s current and target state. The O₂% and He% inputs are always shown; leave He% at 0 for a nitrox target. If the current mix needs draining first, a bleed card shows the bleed-then-fill target. The results then give you:

Blend Required: the composition the panel must produce in the fill line.
Flow Ratios: the O₂%, He%, and Air% of total flow, for setting rotameters.
Analyzers: the O₂ readings to expect on the in-line analyzers. A trimix fill has two readings (an intermediate and the final blend); a nitrox fill has one. For trimix, the Gas Injection Order toggle switches the intermediate analyzer reading between He-first and O₂-first panel layouts.

Inputs and outputs

Pressure and volume follow your unit settings (bar or psi, litres or cubic feet). Oxygen and helium are entered as percentages.

Input	Meaning
Current state	The cylinder’s volume, pressure, O₂%, and He% right now
Target state	The O₂%, He%, and pressure you want to end with
Banks (partial only)	The gas sources you can blend from, Unlimited or Limited. Continuous mode has no banks: its feeds are fixed (Air, O₂, He)
Environment	Altitude, ambient temperature, and fill temperature

Output	Meaning
Plan / steps	The ordered bleed, add-bank, and settle steps (partial) or the blend required, flow ratios, and analyzer readings (continuous)
Achieved mix	The mix the plan actually reaches and its final pressure

Behaviour and limits

The plan assumes your inputs are exact. Analyse what is already in the cylinder before you trust a plan that builds on it; never assume a cylinder’s contents.
Limited banks are respected, so the planner will not propose drawing more gas than a portable bottle holds. Unlimited banks assume an endless shop supply.
Always analyse the finished mix with a calibrated analyser before you breathe it or log it. The planner is a guide to the fill, not a verification of it.

Mix Result is the reverse: it tells you the mix you get from a top-up.
Deco Planner is where you plan the dive these gases are for.

Parts of this guide were drafted with AI assistance and may contain mistakes. It's educational, not a substitute for training. Always dive within your certification and verify with your instruments.