Safety Norms: Data Visualization Techniques

1Purpose, Scope, and Safety Principles

This document sets out safety norms for data visualization techniques, meaning the selection, design, and presentation of charts, maps, dashboards, and similar visual summaries of data. It applies to anyone who selects data sources, transforms datasets, chooses chart types, builds dashboards, publishes visual reports, or presents findings to others. Visualization is mainly an informational and procedural activity, but its errors can still harm people, organizations, and the public.

Three principles guide every rule. Protect the people whose data is shown, including customers, patients, students, and employees. Present data so viewers reach conclusions the data supports. Protect the systems, devices, and accounts used to build and share visuals. Rules labeled mandatory must be followed unless the responsible owner approves a documented exception. Recommendations describe good practice; teams that depart from them should record why.

• Mandatory: no visual may be published without the review step described in this document.
• Mandatory: real personal data may not be used in training or demonstrations unless the data owner approves it.
• Recommended: keep a short written purpose statement for every chart or dashboard.

2Roles, Competence, and Accountability

Accountability for a visualization is shared. The data owner decides whether a dataset may be used for a given purpose and who may see it. The author selects sources, builds transformations, and chooses encodings. An independent reviewer, who did not build the visual, checks numbers, labels, scales, and claims. The privacy or security lead approves any product containing personal, health, financial, or confidential information. Where one person fills several roles, a second qualified person must still perform the review when the output informs a consequential decision.

Competence means more than tool familiarity. Authors must understand how the data was collected, its known gaps, and the definitions of key fields. Work informing clinical, financial, legal, or safety engineering decisions requires subject-matter training, and a chart must never replace qualified professional judgment. Access to restricted data is granted only to named individuals approved by the data owner and ends when those individuals change roles or leave.

• Data owner: approves purpose, sources, audience, and retention.
• Author: documents lineage, filters, calculations, and chart choices.
• Reviewer: confirms accuracy, scale, comparisons, and labeling before release.
• Privacy or security lead: approves personal or confidential content and sharing methods.
• Administrator: removes stale accounts and maintains access logs.

3Course-Specific Hazards and Risk Assessment

The main hazards in data visualization fall into five groups: misleading presentation, disclosure of personal or confidential information, insecure handling of data and tools, harm from decisions made on visual evidence, and physical strain from workstations and display equipment. Realistic triggers are common. A truncated vertical axis can exaggerate a small change. A filter showing one small clinic can imply poor performance that actually reflects sample size. A tooltip revealing a name in a small group can identify a person even when the main chart is anonymous.

Rate every visual before work begins using likelihood and severity, with three levels: low, medium, and high. High-risk work includes any visual informing clinical, financial, legal, safety engineering, or public policy decisions, any dashboard containing personal data, and any external sharing. High-risk work requires documented review by a second qualified person and owner approval before release. Medium-risk internal dashboards need a reviewer and a logged access list. Low-risk illustrative charts still need source citations and a clear label that they are illustrative.

Record each visual in a risk register listing its purpose, data source, hazards, rating, controls, responsible person, and next reassessment step. Reassess whenever the source, audience, tool, or purpose changes.

• Misleading encoding: wrong chart type, non-zero bar baselines, inconsistent scales, or selective time windows. Rating: high where decisions depend on the visual.
• Small-group disclosure: very small cells, unique filter combinations, or detailed tooltips. Rating: high.
• Exposure of files: extracts sent to personal devices, public links, or unmanaged folders. Rating: high.
• Untrusted code: macros, scripts, plug-ins, or files from unknown sources. Rating: medium to high.
• Posture and eye strain: long sessions, poor screen height, or glare. Rating: medium.
• Electrical and cable hazards: display walls, overloaded power strips, or trailing cords. Rating: medium.
• Accessibility exclusion: color-only encoding, low contrast, or missing text alternatives. Rating: medium.

4Preventive Controls and Safe Work Practices

Record the source system, extraction method, collection period, field definitions, known gaps, and every transformation before building a visual. Use only approved sources. Manual edits to source figures are not permitted unless logged in a change record the reviewer can inspect. Mandatory.

Match chart type to the question. Use bar charts for magnitude comparisons and start their value axis at zero. Use line charts for change across an ordered sequence. Avoid three-dimensional effects, which distort perception. Keep scales consistent across panels meant for comparison. Every chart needs a title stating what it shows, labeled axes with units, and a source line. State the denominator for every rate or percentage. Mandatory for titles, units, and sources; recommended for extra annotation.

Show sample sizes beside rates and present comparisons based on very small numbers with a caution or suppress them. Show uncertainty ranges when they have been computed. Do not describe correlation as cause unless a qualified analyst has validated the causal basis and the reviewer has approved the wording. Mandatory.

Apply the minimum group size threshold set by the privacy lead. Thresholds depend on the data, policy, and applicable law, so verify the local value rather than copying one. Remove fields not needed for the purpose and disable tooltips that reveal individuals. Mandatory.

Open files, plug-ins, and scripts only from approved sources. Disable macros in untrusted files. Keep software current through the administrator's patching process. Store transformation scripts in version control. Do not paste restricted data into public converters or generative tools unless the privacy lead has approved that specific service. Mandatory.

Before release, the reviewer confirms that the source matches the documented lineage, that key calculations reproduce on a sample, that scales and labels are correct, that filters are disclosed, and that the title matches the message. Release only after written sign off. Recommended: test on an alternate screen size and with a color vision simulation tool.

Publish only through approved platforms with named recipients and expiring access where available. Do not create public links to restricted dashboards. When presenting, state the source, purpose, main limitation, and whether the visual is provisional. Never present a draft as final. Mandatory for access rules; recommended for presenting caveats.

5Equipment, Environment, Information, and Protective Safeguards

Visualization work uses office workstations, laptops, large display screens, and shared meeting room equipment. Personal protective equipment is not normally required for screen-based work, but the workstation must be assessed. Mandatory: set up workstations under the organization's ergonomic guidance, with the top of the screen near eye level, wrists kept in neutral positions, and lighting that avoids glare. Recommended: take short breaks at intervals set by occupational health staff.

Electrical safety applies to display walls, projectors, and docking stations. Use equipment rated for its load, avoid daisy-chained power strips unless the manufacturer and facilities team approve them, keep cords out of walking paths, and remove damaged equipment from service. Manufacturer instructions and electrical codes are jurisdiction-dependent; verify current versions with facilities staff or a qualified electrician.

Devices must be encrypted, password protected, and locked when unattended. Use privacy filters in open-plan or public areas. Classify each dashboard and file under the organization's scheme and store restricted material only in approved locations. Printed charts with restricted data must be kept in locked storage and destroyed by approved methods. Apply data minimization and retention limits to every dataset.

Use more than color to encode meaning, keep contrast between text and background sufficient for reading, provide text alternatives for images and charts, and test key content with screen readers where the platform supports it. Accessibility duties may arise from laws or contracts; verify current requirements with your legal or accessibility office.

6Incident Reporting, Emergency Response, and Escalation

Report every incident, near miss, and error, including published visuals later corrected. Incidents include privacy exposure through a dashboard or export, a lost or stolen device, suspected malware, use of an unapproved tool with restricted data, a misleading chart used in a decision, and workstation injury. Reporting is expected without blame. A prompt report is a safety action.

For data incidents, stop further distribution by disabling the link or dashboard if you have permission. If you do not, escalate immediately. Do not delete files, logs, or messages, because they are evidence. Notify the privacy or security lead as soon as possible and within any timeframe in organizational policy. Record what was shown, to whom, and for how long. Notification duties to regulators or individuals depend on applicable law; verify with counsel.

For physical or medical emergencies, call emergency services or the on-site emergency number. Do not move an injured person unless the scene is unsafe. Only trained first aiders should provide first aid. If equipment smells of burning or sparks, unplug it only if this can be done without contact with a live source; otherwise call facilities or emergency services. This guidance is educational and does not replace approved emergency procedures.

If a misleading or erroneous visual was distributed, issue a correction to all recipients stating what changed and why. Retain both the original and corrected versions, and notify decision makers through the data owner.

• Level 1: author or reviewer fixes a minor error before release and logs it.
• Level 2: owner and privacy or security lead are notified promptly for any published error or exposure.
• Level 3: executive and legal leads are notified for any personal data breach, regulated decision error, or public release error.

7Records, Training, Inspection, and Review

Maintain a register listing each visual's owner, purpose, source, risk rating, reviewer, approval record, access list, and retention. Keep change logs and version control history for transformations and calculations. File incident reports and corrections with the related visual. Retention periods depend on policy and law; confirm them with records management staff.

Before receiving restricted data access, each author completes training on the tool, data classification, privacy basics, chart integrity, accessibility, and incident reporting. Reviewers also complete training in statistical checks and sign-off procedures. Refresher training should follow the organization's schedule and occur whenever tools, policies, or laws change.

Administrators and privacy leads inspect dashboards to find stale access, public links, unreviewed content, and unused exports. Inspection frequency should match risk. Track corrections, overdue access removals, and near-miss reports. Rising near-miss reporting, followed by corrective action, indicates a healthy safety culture.

Review these norms at a fixed interval set by the safety committee and after any significant incident, tool change, or change in applicable law. Confirm that the rules still match practice, thresholds remain appropriate, and references to laws and standards are current. Verify external standards with the issuing body or a qualified professional.

Implementation checklist

• Confirm the data owner approved the purpose, source, and audience before building.
• Record lineage, filters, and transformations in the visual register.
• Check axes, scales, units, labels, and sample sizes against the source.
• Apply the approved small-group threshold and remove identifying detail.
• Verify that titles and caveats match the conclusions shown.
• Confirm color is not the only encoding and that text alternatives exist.
• Share only through approved platforms with named, expiring access.
• Report errors, exposures, and near misses to the owner and privacy lead promptly.
• Confirm workstation and cable arrangements meet local ergonomic and electrical guidance.
• Schedule the next access review and risk reassessment.