Open Path Lasers Versus Point Sensors for Chemical Detection

Facilities have traditionally detected toxic gases and chemical threats through the use of "point sensors." Point sensors are small portable or fixed-mounted devices that protect a single local area, similar to a carbon monoxide detector in your home.

When a toxic chemical gas comes into contact with the sensor, a chemical match can be made and alarms can be sounded. To improve the likelihood of detection, point sensors often draw surrounding air into the instrument's measurement chamber using an air pump.

Point sensors use many detection technologies, including electrochemical sensing, FTIR spectroscopy, IMS, and GC/MS. However, all point sensors require that gas comes into contact with the sensor. This costs valuable time for those at risk.

Each individual point sensor is only able to cover a small area. Demonstration tests have shown that by the time that a chemical threat reaches the sensor, hazardous chemicals may have circulated widely for many minutes.

In order to expand coverage, some facilities install large numbers of point sensors. These are often networked together using radio waves or cabling. An indoor space may require dozens of these sensors — each of which is expensive, requires regular maintenance, and may include routine replacement of costly consumables.

You can see in the illustration below that each sensor is drawing air from its immediate environment (red cones). Hazardous chemicals are not detected until they waft to the sensor's sampling point.

chemical point sensors

An alternative to networks of point sensors is an "open path laser" solution.

An open path system uses an infrared laser to create an invisible "chemical trip wire." Chemicals that cross the laser beam path can be detected and identified in seconds, even at long distances.

In open-path systems, chemicals do not need to touch the instrument itself; they simply need to come into contact with the laser beam. Because the beam traverses the space looking for gases, open path lasers allow for near-instantaneous detection of chemical threats at distances of hundreds of meters away.

Open path lasers have been used for many years to monitor refineries and oil wells for escaped gases, or "fugitive emissions." Capitalizing on this proven and effective detection capability, Block Engineering has developed a quantum cascade laser-based open path system that scans for dozens of toxic industrial chemicals (TICs) and chemical warfare agents (CWAs) simultaneously.

The invisible, eye-safe laser can be reflected to create blanket coverage or angle around corners to handle unusual indoor layouts. By covering such large areas, a single open path sensor can effectively protect the same space as a handful of point sensors, at a fraction of the cost and with dramatically reduced response time.

Because the open path technology does not draw in the ambient air, the LaserWarn requires minimal maintenance while running unattended 24/7. The system does not contain air pumps, filters, or other consumables.

Below is a sample beam path for the LaserWarn. The laser can be angled to cover a hallway as well as turn a corner. Detection can be made at great distances in seconds.

open path chemical detection

Block's application engineers can work with you to create beam paths that are customized to your unique facility layouts. The system can be packaged for both indoor and outdoor environments.

In addition, the LaserWarn is designed to deconvolve complex chemical combinations that simple electrochemical solutions cannot, even in the presence of "masking agents" designed to confuse sensors.

We would be happy to discuss our LaserWarn open-path QCL system with you. Please contact us to schedule a conversation.