Security Smoke Screens: How Intruder Fog Systems Work
What a smoke screen does, where it earns its place, and how it ties into an alarm
A security smoke screen is a fog generator linked to your intruder alarm. When the alarm confirms a break in, the unit fills the protected room with a dense, harmless fog so an intruder cannot see what to take and usually leaves empty handed. It does not replace an alarm; it adds an active layer that works in the short window before anyone can respond.
Most burglaries are over quickly. An alarm tells people something is wrong, but it cannot stop a determined thief grabbing stock from a shelf or a laptop from a desk. A fog system changes that by removing sight of the room itself. The fog is typically produced from a glycol based fluid heated inside the unit, and quality systems are designed to leave no residue on stock, electronics or furnishings.
Smoke Screen is one of the brands we work with, and we connect fog units to the alarm panel so they only fire on a genuine, confirmed activation. The rest of this guide covers where a smoke screen makes sense, how triggering is set up to avoid false deployments, and the questions worth asking before you commit.
Why It Happens in the First Place
Why fog stops theft
Thieves rely on being able to see. Once visibility in a room drops to almost nothing, finding and carrying goods becomes guesswork, and most intruders leave rather than stumble around blind while an alarm sounds.
How triggering avoids false deployment
Units are normally set to fire only on a confirmed alarm, for example two separate detectors activating in sequence, rather than a single sensor. That reduces the chance of fog being released by a spider, a draught or a pet.
Why room size and airflow matter
A unit sized for a small office will not fill a large warehouse bay. Airflow from extractors or open shutters disperses fog quickly, so positioning and output have to be matched to the actual space.
Why it is linked to the alarm, not standalone
Tying the fog unit to the alarm panel means it follows the same set and unset routine staff already use, and the alarm event log records exactly when the unit was triggered.
Why fire safety is considered first
Fog must never block a protected escape route or confuse a fire detection system. Units are positioned away from escape routes, and smoke detectors in the protected area need to be considered at the design stage.
How It Tends to Show Up
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Step by Step, Safely, at Home
Pick the room that really matters
Fog works best in a defined space such as a stock room, a shop floor behind the counter or a single office. Walk the premises and decide where a thief would head first; that is usually the room to protect.
Check how your alarm is set up today
A fog unit needs a reliable trigger. Note your alarm panel make if you can see it on the keypad, and whether the system is monitored or bells only, so an engineer can confirm how the unit will be wired in.
Think about who is on site out of hours
Cleaners, early deliveries and staff who open up need to understand the system. Plan who sets and unsets the alarm so the fog is never armed while someone is legitimately inside.
Look at ventilation and doors
Open vents, gaps under doors and very large open plan spaces thin the fog out. Measure the room roughly and note any openings so the unit can be sized and positioned properly.
Tell your insurer and landlord
It is good practice to let your insurer know a fog system is fitted, and in rented premises to get the landlord's agreement before any unit is mounted to walls or ceilings.
Straight Answers to Common Questions
Security Smoke Screens: How Intruder Fog Systems Work: common questions
Stop Here and Get an Engineer Out
Keeping it from coming back
Treat a smoke screen as the last layer, not the first. Good locks, a well set alarm and visible CCTV deter most attempts; the fog unit is there for the rare occasion someone gets inside anyway. Have it checked during your regular alarm service so fluid levels, batteries and trigger wiring are all confirmed.
Related Guides Worth a Look
- How to Choose a Burglar Alarm Company
- Business Security Systems: A Practical Guide
- What happens on installation day and what makes a job quicker or longer
- Security System Survey: What to Expect
- Burglar Alarm Going Off For No Reason: Why
- How Orisec user codes work, what causes a lockout, and when an engineer reset is needed
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