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A guide to people flow sensors

In the past, the only way to tell how many people were entering and leaving a room was to physically count people as they passed – a very tedious and error-prone method. Today, technological solutions such as cameras, sensors, and trackers have made this much easier and more accurate.

Now, more than ever, it’s important for building owners and facilities managers to have a good understanding not just of the number of people in their building, but in specific spaces like meeting rooms, canteens and bathrooms.

As the name suggests, a people flow sensor monitors the ‘flow’ of people as they walk towards or away from the sensor. This means you know, in real time, how many people have entered and exited the room.

As employees return to the workplace, this data can help determine high traffic entry or exit points, busy areas which may need extra cleaning, and identify if social distancing is possible. But moving beyond Covid, savvy managers know that fully optimising their spaces can help with resource planning, generate energy savings and save costs.

And receiving accurate, real-time information means you can make highly informed decisions about how you can best use your workspace and manage facilities.

Here, we’ll explore how people flow sensors work, what the key differences are between them and how to choose the right one.

What are people flow sensors?

These sensors provide real-time data on the bidirectional flow of people in and out of a space.

The data from people flow sensors can be used to count how many people have entered/exited a space. This insight can be used to:

  • Determine peak times and levels of usage
  • Spot behavioural trends
  • Optimise utilities usage

You can also view data such as which times of day or days of the week generate more traffic than others. From here, you know, for example, when you need to have cleaning staff and supplies on hand.


Types of people flow sensors

People flow sensors are a simple yet powerful tool to optimise workspace strategies and support healthy buildings. But data-based decision-making will only be as good as the quality of the data you work with. Not all sensors are born equal.

Here are some of the pros and cons of each:


Time of flight sensors

The simplest and least expensive option. These sensors emit an infrared light beam that reflects off a person and returns back to the sensor. The time taken to return gives an accurate distance calculation. The sensor uses these movements to determine if the person is moving away from or towards the sensor.

Pressac people flow sensor

Pressac people flow sensor

Data can then be fed into workspace management software to report people flow in/out of a room in real-time or count how many people have entered or exited a room.


  • Inexpensive as there is no costly camera technology
  • More accurate, as they’re less likely to pick up reflections in glass or screens
  • Quick and easy to install — they can be powered by USB or ethernet
  • Simply pick up movement, not images — so there are no privacy issues


  • The beam range can be limited to smaller spaces and these are not the best options for very wide entrances and large spaces
  • Can’t detect multiple people moving close together (so not suitable for counting high traffic and for spaces with small children)

They can be mounted on a door frame to measure the flow of people coming into and out of a meeting room, cubicle or restroom.


Thermal (PIR) counting sensors

These sensors use heat from people’s bodies to track when they enter and move around a building. They receive thermal signals from their surroundings and can tell when these are interrupted by human presence.


  • Provides data on multidirectional movement of people inside and outside a building
  • Unobtrusive and easy to install
  • Low maintenance
  • Cost-effective


  • More expensive option
  • Some have been shown to have some data inaccuracies — the lower resolution and field of vision can make it harder to distinguish between adults and children, which may affect demographic accuracy
  • People must be in motion for the sensor to capture their signal and effectively ‘count’ it as a person
  • External weather conditions may inhibit accuracy


Video sensors

This type of sensor uses video to track foot traffic in a building. They read visible light from within the electromagnetic spectrum and can identify outlines of faces or bodies to indicate the number of people in a space.


  • Can cover a wide area and more detail can be gathered when combined with multiple video-based units
  • Offer a much more accurate picture than passive infra-red sensors


  • Much more expensive than passive infra-red and time of flight people flow sensors
  • Requires more complex algorithms to get the sensor working
  • Some video sensors accuracy can be affected by reflections, shadows, backgrounds and inconsistent light levels, which can lead to miscounts
  • Can lead to concerns around privacy

They work best in environments with consistent lighting and provide highly detailed information about the number of people entering and moving around a building.


How to make the right choice

Most businesses will benefit in some way from using a people flow sensor. But if you’re buying one for the first time, or upgrading your existing technology to improve analytics, it’s essential that you choose the right kind.

What you need is accurate, consistent and reliable data that you can trust. Many manufacturers will boast of ‘90% accuracy’ which can draw you in. But then you discover this is on average — so while there are times of excellent accuracy, there are also times when this number dips well below what you need. Consistency is key here — data derived from peaks and troughs won’t help you make the right decisions.


Integrating people flow sensor data

The data you receive is the direction flow, which will tell you how people move around a space — essentially if they are seen entering or exiting.

This data is sent from the sensor to a system that knows what ‘in’ means and what ‘out means. If you have multiple entry and exit points, you need to collate the data from all sensors. What it ultimately comes down to is how many ‘ins’ and how many ‘outs’ they’ve recorded — the difference will be the people count.

Because our technology is platform agnostic, the data from our people flow sensors can be used in any way you need:

  • Data can be sent securely – via Ethernet, LTE (4G) or WiFi – locally or to your cloud using our smart gateway
  • You can access near real-time data through any MQTT broker, IBM Watson, Microsoft Azure, AWS loT platforms
  • We have a growing number of pre-built connections with leading platforms and workplace management systems, plus a Google Sheets option for simple data reporting
  • Sensor data can be used in systems with protocols such as Modbus and BACnet, letting you monitor, control and report within an existing building management system
  • Sensors can connect directly to smart actuators, allowing you to automate room controls

Reaping the benefits of smart technology

By integrating people flow sensors into your workspace solution you can improve space planning, implement smarter working, and optimise facilities management based on actual usage, as well as support demand-driven controls. In turn, this leads to a more healthy and pleasant working environment. Good for everyone.

As technology advances, you can access multiple types of occupancy monitoring sensors for collecting data. Each has its advantages and disadvantages, so it’s important to work with a smart sensor expert when making your decisions.

Contact our IoT business development team to see how we can support your workplace management solution by integrating smart sensors.

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