Security 51 Security Check Guide: Complete Day 1-14 Walkthrough

Getting Started with Security 51

Security 51 drops you into the role of a security officer stationed at a mysterious facility where visitors range from ordinary humans to entities with bizarre anomalies. Your job sounds simple—verify identities, scan for irregularities, and decide who passes through—but the complexity ramps up quickly. This Security 51 security check guide is designed to help you navigate every shift from Day 1 through Day 14 with confidence, covering each tool, instruction set, and strategy you'll need.

The first level spans 14 in-game days, during which you gradually unlock new scanning equipment, monitoring interfaces, and research capabilities. According to player experience, visitors are randomized, so while the specific people you encounter may differ, the rules and tools remain consistent. Whether you're a new hire or replaying for a better score, this Security 51 security check guide breaks down everything you need to maximize earnings and minimize mistakes.

You can check out the game for yourself on its official Steam page for additional details and updates.

Core Mechanics Every Officer Needs to Know

Before diving into the day-by-day breakdown, it's important to understand the foundational systems that govern every shift in Security 51.

Reading the Daily Instructions

Each day begins with a set of instructions posted at your desk. These dictate exactly how to handle different types of anomalies and document issues. The instructions follow a priority hierarchy:

The key takeaway: always read instructions carefully before starting your shift. The game pauses while you review them, so there's no rush.

Managing Your Shift Length

Starting on Day 2, a 24-hour clock tracks how long your shift runs. Completing tasks efficiently and ending your shift quickly earns you a bonus. Conversely, wrong decisions incur penalties that dock your earnings.

Understanding the Three Core Actions

• Approve (Green): Drag the access card and punch the green section to let a visitor through.
• Deny (Red): Punch the red section when a visitor fails to meet entry requirements.
• Call Security: Used for serious anomalies like forged documents or internal irregularities. Denying someone when you're supposed to call security results in a penalty.

Essential Tools Unlocked Across Days 1-14

Your arsenal of diagnostic equipment grows steadily throughout the first level. Here's a complete breakdown of every tool, when it unlocks, and what it detects:

Day-by-Day Breakthroughs and Strategies

This section of our Security 51 security check guide highlights the most critical developments and strategies for each day, focusing on what changes and how to adapt.

Days 1-3: Learning the Ropes

Day 1 is essentially a tutorial—a simulation that your supervisor reveals was just practice when Day 2 begins. On Day 2, you unlock the X-Ray Scanner and learn about shift length mechanics. Day 3 introduces the "Call Security" action, triggered by fake names on passports or external neck anomalies.

Critical tip for Day 3: Body anomalies are acceptable as long as they're not on the neck. Denying access when you should call security will penalize you.

Days 4-6: Photography and Isolation

Day 4 unlocks the Polaroid camera. When photographing visitors, watch for static blur—it indicates a photo anomaly is present. Wait for the film to develop before making your decision.

Day 5 introduces medical certificates. Use the X-Ray Scanner to detect external anomalies, then ask for documentation. Forged certificates require calling security, while authentic ones with anomalies still result in denial.

Day 6 is a major milestone. Your clearance level increases, and you gain access to the Isolation Ward. You can now monitor the elevator camera as visitors leave, switching between Night Vision and Thermal Imaging to spot anomalies like fungus. Isolated visitors can be used for research.

Days 7-9: Citywide Monitoring and Thermal Scanning

The Citywide Monitoring Interface adds a strategic layer. You must complete Field Operations before the Unknown Disease reaches a danger mark. These operations consume Sanity, so balance is essential. You can only perform one operation per day, and successful research at the Isolation Ward unlocks additional operations.

Days 10-14: Advanced Anomalies and Final Challenges

Day 10 introduces the Handbook and the Phantom Hound anomaly. Photograph each visitor and look for the specific anomaly pictured in your Handbook. If static appears, move the camera to find the area with the most distortion before taking the shot.

Day 11 brings the Bone MRI Scanner. Use it to inspect the skeleton, ask for medical certificates when anomalies appear, and call security if documents are forged.

Days 12-14 layer multiple tools and rules simultaneously. Here's a summary of the instruction complexity:

Day 14 is the final shift of Level 1 and requires juggling three different scanning tools. Community reports suggest this is where most players make their first significant mistake, so take your time with each visitor.

Pro Tips for Maximizing Earnings and Minimizing Mistakes

Buy Strategically

Every day ends with an earnings report and a shop. Prioritize upgrades that expand your scanning area or reduce development time. Here's what experienced players recommend purchasing early:

Sanity Management

Field Operations drain your Sanity, which can impact performance. Based on player experience, here are effective strategies:

• Always keep at least two sandwiches in your inventory
• Purchase sedatives starting around Day 8 when shifts get longer
• By Day 14, consider upgrading to Street-Style Noodles and entertainment items like B-Movie Action Flicks for better sanity recovery
• Conduct research at the Isolation Ward regularly to unlock new, more efficient Field Operations

Elevator Camera Discipline

From Day 6 onward, checking the elevator camera becomes a critical habit. Every time the lift returns, switch between Night Vision and Thermal Imaging to catch anomalies in departing visitors. On days when the Isolation Ward is inaccessible (like Day 7), you must Exterminate anomalous visitors instead of isolating them.

Instruction Priority Hierarchy

The most common mistake players make is applying rules in the wrong order. When a visitor has multiple issues, always follow this priority:

1. Let Through overrides (photo anomalies, hyperthermic areas, brain anomalies) take precedence over everything
2. Call Security triggers (forged documents, specific organ/bone anomalies) come next
3. Standard deny/approve rules apply only when no higher-priority conditions are met

FAQ

What is the most important thing to remember in this Security 51 security check guide?

Always read the daily instructions before starting your shift. The game pauses while you review them, and the priority hierarchy changes every day. Misapplying rules—like denying someone when you should call security—is the most common cause of lost earnings.

Do I need to check every visitor with every tool?

Not necessarily. Each day's instructions specify which anomalies matter. For example, on Day 3, body anomalies are acceptable unless they're on the neck. However, from Day 6 onward, always check the elevator camera for departing visitors, and from Day 10, photograph everyone to catch photo-based anomalies.

How do Field Operations and Research work together?

Field Operations are accessed through the Citywide Monitoring Interface (unlocked Day 7) and consume Sanity. You can only perform one per day. Research at the Isolation Ward unlocks new Field Operations, creating a progression loop. Prioritize research early to expand your operational options for later, more complex days.

What should I buy first with my earnings?

Stock up on sandwiches immediately—they're cheap and essential for sanity recovery. Then prioritize tool upgrades that expand scanning areas, starting with X-Ray (Area) on Day 3 and Polaroid (Development Time) on Day 4. Save higher-tier upgrades like MRI area expansions for their respective unlock days.