How to Block Motion Sensors? Let’s Find Out

Motion sensors can be quick to throw cold water on ideas to surprise your loved ones. This is especially the case when you don’t have control over the sensor or can’t shut it off. Since raising an alarm isn’t an option, blocking the motion sensor might be a sound option. 

If the thought of temporarily blocking a motion sensor has crossed your mind, read ahead as we explore how to block motion sensors.

How to Block Motion Sensors?

Motion sensors can be blocked by avoiding their trigger mechanisms. Most sensors today work on infrared radiations (heat) to trigger alarms. Covering the lens of the sensor with an insulating piece of material can easily bypass or block it. 

However, this solution is true for passive infrared sensors only. Today, motion sensors are available in several types including ultrasound, infrared, microwave, dual-technology, or magnetic sensors.

Some characteristics are still true for every type of motion sensor. These detection devices have a semi-circular field of view, meaning they can cover entire rooms easily. However, incorrect placement by homeowners can often leave blind spots which can be exploited.

Let’s discuss blocking each type of motion sensor in detail, next:

How to Block PIR Motion Sensors

PIR motion sensors rely on changes in heat signals across a room. If an object releases heat, the sensor is triggered and an alarm is raised. So, the trigger mechanism here is infrared radiation. 

To block a PIR motion sensor, you’d have to cover the lens of the camera or a heat-emitting object with an insulating material. The insulating material would contain the heat and avoid triggering the sensor. 

Pet-friendly motion sensors, which also rely on infrared radiations, are easier to block as they monitor a shorter vertical range. So, if one were to crouch away from a sensor-enabled hallway, it’s probable the sensor never triggers.

How to Block Microwave Motion Sensors

Alternatively, you might be facing a microwave motion sensor. It sends out microwaves, invisible to the eye, and detects reflections in the room. Ultrasound sensors work the same way such that they send out sonar (audio) waves to detect reflections from a moving object.

A simple yet effective solution against microwave sensors is to use aluminum foils. The foil absorbs waves effectively and doesn’t reflect the waves – so the sensor is ultimately bypassed. 

How to Block Door Sensors

Apart from these motion sensors, you might be facing a door or window sensor. These sensors generally operate with a magnet attached to both the window and the frame. Once the circuit breaks i.e., one of the magnets moves away, an alarm is triggered. 

Door and window sensors can be bypassed by a strong magnetic presence. The magnet overpowers the existing magnets and simply shuts them down making the sensors dysfunctional. 

Let’s explore more methods to block motion sensors, next! 

Ways to Block Motion Sensors

To block a motion sensor, you’d have to observe its type, placement, field of view, and any blind spots. Once done, blocking motion sensors is all about blocking their trigger mechanisms. For PIR sensors, it’d be avoiding heat radiations whereas for magnetic sensors, it’d be the circuit break of the two magnets.

Let’s take a look at a few ways to block different types of sensors:


Styrofoam is an excellent insulator. It effectively limits heat and can be a sound defense against a motion sensor. But covering yourself with a styrofoam sounds a little too excessive. However, it’s still an option if you were to walk the mile.

Aluminium Foil

Aluminum foils are one of the best ways to block a motion sensor. Aluminum has the capability to fully block radio as well as other electromagnetic waves due to its strong conduction properties. Covering the lens of the sensor effectively reduces the sensitivity of the sensor and ultimately blocks its vision. 

Strong Magnetic Field

This one’s for door and window sensors in particular which rely on magnetic strips to work. Both the door and the frame have a strip which are joined together to form a circuit. Breaking that circuit causes a trigger.

However, this design is fairly simple and vulnerable to the presence of a strong magnetic field. If you were to introduce another magnet with a stronger magnetic field, the sensor would simply fail to work.

Pointing Infrared Light at Lens

This might sound like a bad idea but pointing a stable beam of infrared wave (or a light of a similar wavelength) can also reset the sensor. You’d have to keep pointing the light towards the lens until it’s dysfunctional and you can then walk around the room.

However, not every motion sensor follows this reset mechanism and pointing a beam of infrared radiation might just trigger the sensor.

Electrical Tapes

Black electrical tape has also proven to block a motion sensor in many cases. Once you’ve made it safely to the sensor without tripping it, start placing the tape from the edge and slowly cover it completely.


Pieces of cardboard can help limit the field of view of the sensor. Raise it against the lens of the camera and attempt to block its sight. If the piece of cardboard isn’t thick enough or the sensor can view through it, the sensor won’t be blocked effectively. 

FAQs on How to Block Motion Sensors

Blocking motion sensors isn’t as easy as it seems. Though we’ve covered a few ways to do so, you might still have a few questions. Let’s explore answers to some of the most commonly asked questions on ‘how to block motion sensors’:

Can you cover a motion sensor?

Covering a motion sensor is effective in blocking it if the material doesn’t let the waves pass through. Aluminum foils are helpful against microwave motion sensors. Similarly, cardboard pieces, black electrical tapes, and styrofoam are helpful against PIR motion sensors.
If the material lets the waves pass through, an alarm would trigger instantly. You should have knowledge of the type of the motion sensor before attempting to cover it. Otherwise, it’s likely the sensor will go off due to incorrect blockage. 

How do you turn off motion sensors?

You can turn off your motion sensor by removing the batteries, switching it off, or unmounting the sensor from the wall. Some sensors require a little more work to turn them off such that you’d have to disconnect them from the panel by undoing the wiring.
Blocking the motion sensor’s field of view would also turn it off temporarily. We’ve discussed several ways to do so. Aluminum foils and black electrical tapes are the most effective against motion sensors.

What is the difference between an active and passive motion sensor?

Active motion sensors transmit waves or signals across the field of view to detect objects. On the other hand, passive motion sensors (usually infrared sensors) detect motion based on changes in heat across the room without transmitting any waves.
Ultrasonic sensors are one of the most common types of active motion sensors. These operate by sending out sonic waves and detect objects if there’s a reflection. Similarly, passive infrared sensors fall under passive sensors and trigger alarms if a heat-emitting object enters their field of view.

In conclusion, blocking a motion sensor would require preexisting knowledge of the sensor and the environment. Hopefully, with good intentions, you’d be successful in utilizing some of the ways we’ve discussed to block a sensor.