Understanding ISA-101

Introduction

Before we get started, I want to make one thing clear:
I do not own a paid copy of the official ISA-101 standard. ISA-101 is a copyrighted document and is not freely available online. Everything written in this article is based on:

• publicly known industry practices
• real-world SCADA/HMI design experience
• common high-performance HMI principles
• my daily work with Ignition Perspective, AVEVA OASys, and other platforms

This article is my own interpretation and simplified explanation of ISA-101 principles — not a reproduction of the official text.

If you want the formal, exact standard, you can purchase it directly from ISA:
🔗 ANSI/ISA-101.01-2015, Human Machine Interfaces for Process Automation Systems

My goal here is to help SCADA developers, integrators, engineers, and designers understand how these principles apply to modern industrial HMI design.

What Is ISA-101?

ISA-101 is an international standard that defines best practices for creating safe, effective, and high-performance Human-Machine Interfaces (HMIs) in industrial automation.

If you design operator screens — tanks, pumps, P&ID-style flows, graphics, faceplates, navigation structures — ISA-101 is the design rulebook you use to ensure:

• clarity
• consistency
• situational awareness
• operator efficiency
• safe decision making

Think of ISA-101 as the foundation for modern SCADA/HMI design.

Why ISA-101 Exists

Traditional HMIs from 15–20 years ago were:

• overly colorful
• visually noisy
• inconsistent across plants
• hard to interpret under pressure

Operators were constantly scanning bright screens full of greens, blues, reds, shadows, gradients, and animated icons.
Real alarms blended into the chaos.

ISA-101 was introduced to solve this.

The Standard Specifically Addresses:

1. Too Much Color

Old HMIs used bright colors for everything — normal state, running state, pipe colors, tank colors.
Operators suffered visual fatigue.

2. Poor Situational Awareness

Operators could not quickly see where a problem was coming from.

3. No Consistency

Symbols, colors, navigation, alarm behavior — everything changed between sites.

ISA-101 fixes these using clear rules for:

• layout
• color usage
• navigation
• alarm handling
• symbol consistency
• display hierarchy

What ISA-101 Covers

ISA-101 defines four major documentation sets:

1. HMI Philosophy

This is the high-level document describing:

• plant-wide rules
• user roles
• color definitions
• how alarms appear
• font rules
• naming conventions
• navigation strategy

Think of it as the “constitution” for all HMIs on site.

2. Style Guide

This is the designer’s toolbox. It contains:

Typography

Sans-serif fonts recommended:

• Segoe UI
• Roboto
• Helvetica
• Open Sans

Font usage guidelines:

• Titles: 16–20 pt
• Values: 12–16 pt
• Units: 10–12 pt
• Avoid decorative fonts
• Avoid ALL CAPS except for alarms

Color Palette (High-Performance HMI Palette)

ISA-101 encourages a neutral, grayscale-first design.

Neutral Greys (Normal operating conditions)

• Light Grey: #D9D9D9
• Medium Grey: #A6A6A6
• Dark Grey: #6E6E6E

These colors keep the screen calm.

Use Color Only When Necessary (Abnormal Conditions)

Color in ISA-101 is reserved for highlighting abnormal or operator-action conditions. The base colors below represent the standard meanings, but high-performance HMIs typically use muted or desaturated tones until severity increases. This prevents visual overload and ensures that truly abnormal conditions stand out immediately.

Condition	Meaning	Standard Color	Muted (Recommended for Normal Display)
Critical Alarm	Unsafe	Red (#FF0000)	Muted Red (#D64545)
High Alarm / Approaching Limit	Caution	Orange-Red (#FF4500)	Muted Orange-Red (#E97B40)
Warning	Needs attention	Amber (#FFC000)	Muted Amber (#E4B74E)
Manual Mode	Operator override	Blue (#0096FF)	Muted Blue (#5A96D6)
Running	Normal	White (#FFFFFF)	— (Neutral gray tones used for normal operation)
Stopped	Idle	Black (#000000)	Soft Black (#3A3A3A)
Maintenance / Bypass	Not in service	Purple (#A020F0)	Muted Purple (#9D6AD1)

Standard Colors

Muted Colors

Color Philosophy Summary

• 90% of the screen should remain neutral (grayscale).
• Color means “Look here now.” It draws attention to abnormal or operator-relevant states.
• Saturation indicates severity: muted or low-intensity versions of each color are used for early-stage states (e.g., low warning), while full saturation is reserved for higher severity.
• Muted colors reduce visual noise. By desaturating the base colors, normal operating screens remain calm and readable, allowing alarms and warnings to stand out instantly. Muted colors help prevent alarm flooding and reduce operator fatigue, supporting the ISA-101 goal of improving situational awareness.
• Full-color intensity is used only when necessary, such as critical alarms or urgent operator action conditions.

Symbol Library (Reusable SVGs)

All equipment icons must be:

• consistent
• simple
• clean
• color-coded by state only
• free of 3D shading
• uniform across all displays

You already follow this in your designs.

3. HMI Toolkit

Reusable blocks such as:

• pump templates
• valve templates
• line arrows
• sensor tiles
• KPIs
• sparkline charts
• alarm banners
• navigation bars
• pop-up control faceplates

These ensure screens are built quickly and consistently.

4. Display Design Levels (Hierarchy)

ISA-101 supports four HMI display levels, each with a specific purpose.

ISA-101 Display Hierarchy

Level 1 – Overview Display

Purpose: See problems instantly.
This is the “plant at a glance.”

Shows only:

• KPIs
• sparkline trends
• major alarms
• process health
• production goals
• critical bottlenecks

No details, no setpoints.

Think of it as your dashboard health monitor.

Level 2 – Process Area Display

Purpose: Supervisory control.

Shows:

• major equipment
• flow paths
• valve states
• alarm badges
• basic trends
• area navigation

Used for startup/shutdown procedures and operator workflows.

Level 3 – Unit Control Display (Pop-Up)

Purpose: Fully control a single piece of equipment.

Includes:

• PID controls (PV, SP, CV)
• Mode switching (Auto/Manual/Cascade)
• Interlocks
• Detailed trends
• Alarms for that equipment
• Manual control buttons
• Nameplate information
• Diagnostic texts

Level 4 – Diagnostics / Maintenance Display

Purpose: For maintenance techs.

Shows:

• raw I/O
• tuning parameters
• calibration offsets
• drive diagnostics
• network status
• advanced settings

Operators are not meant to use Level 4 except with supervision.

ISA-101 Color Rules

Color Rules for Equipment

Pumps

• Grey → stopped
• White → running
• Red border → alarm
• Amber border → warning
• Blue → manual mode

Valves

• White → open
• Grey → closed
• Yellow → fault
• Blue → manual

Transmitters

• Grey body
• Thin colored border depending on alarm state

Pipes

• Light grey when idle
• Darker grey when flow is active
• Never use bright colors for normal flow

Alarm Visualization

Alarm Visibility Rules

• Use animation (blink) only for unacknowledged alarms
• Use solid colors for acknowledged alarms
• Put alarm badges next to equipment
• Include alarm counts (ex: 3 ALM)
• Show the highest severity alarm first

Severity Examples:

Severity	Behavior
Critical	Flashing red
High	Solid red
Medium	Amber
Low	Grey icon

Why ISA-101 Matters

ISA-101 improves:

• operator reaction time
• consistency across screens
• safety
• alarm prioritization
• cognitive load
• operator training

It also gives SCADA developers a framework for building cleaner, more professional HMIs.

How I Use ISA-101 in My Designs

In my current work:

• 90% of my UI uses neutral grey backgrounds
• All color is reserved strictly for alarms or manual modes
• I use consistent and simplified SVG icons
• KPIs and sparkline tiles follow high-performance HMI guidelines
• Navigation follows the Level 1 → Level 2 → Level 3 workflow
• Alarm badges follow consistent color & severity rules
• All trend tiles use minimal styling for clarity

These align naturally with ISA-101 principles.

Conclusion

ISA-101 is not a style template — it is a set of design principles that help operators make safer, faster decisions.
Following it transforms your HMI from “pretty graphics” into real operator tools that enhance performance and reduce risk.

With or without access to the official standard, understanding these core ideas
will help you design HMIs that are modern, efficient, and operator-focused.

Disclaimer

This article is an independently written summary based on publicly available information and my professional experience. It is not endorsed by the International Society of Automation (ISA). For the official ISA-101 standard, please refer to the published document available for purchase on the ISA website.

References

ISA – International Society of Automation. (n.d.). ISA101, Human-Machine Interfaces. Retrieved from ISA – International Society of Automation: https://www.isa.org/standards-and-publications/isa-standards/isa-standards-committees/isa101

Malisko. (2024, May 07). Unpacking ISA-101: Beyond the Misunderstood Grayscale – A Closer Look at HMI Levels and Their Importance. Retrieved from Malisko: https://malisko.com/isa-101/

O’Brien, L. (n.d.). How ISA-101 Lifecycle Standard Improves Operator Effectiveness with Display Design and Lifecycle Management. Retrieved from ARC Advisory Group: https://www.arcweb.com/industry-best-practices/how-isa-101-lifecycle-standard-improves-operator-effectiveness-display

Schirn, A. (2025, October 03). ANSI/ISA 101.01-2015: HMIs for Process Automation Systems. Retrieved from ANSI American National Standards Institute: https://blog.ansi.org/ansi/ansi-isa-101-01-2015-hmi-for-process-automation/

Yokogawa Canada, Inc. (2015). ISA-101: Toward a More Effective HMI Strategy. Retrieved from YOKOGAWA Co-innovating Tomorrow: https://www.yokogawa.com/ca/library/resources/media-publications/isa-101-toward-a-more-effective-hmi-strategy/

Hongke Industrial IoT. (2022, November 3). SCADA in digital factories: HongKe Panorama SCADA solution. CSDN Blog. https://blog.csdn.net/Hongke_IIOT/article/details/127664136