Artificial noses – are they too costly?

The first two articles of this series gave insight into the emission monitoring methods as they can be found in international regulations from the IMO and EU. This article will examine a new and upcoming monitoring method.

At present, the most accurate determination of fuel Sulphur content via a ship external approach is provided by “artificial noses”, commonly known as sniffers. These sensors are capable of measuring the emissions in the exhaust gas plumes of ships and can be installed in airborne or land-based positions. Specifically, they measure the SO2 and CO2 levels, making it possible to calculate the sulphur content of the fuel that is being used on-board.

1. Drones

Unmanned Aerial Vehicles (UAVs), commonly known as drones, can be fitted with sniffers. As a matter of fact, drones have been used to verify compliance with SOx regulations in the European Emission Control Areas for some time now.

What are the dis-/advantages?

The main advantage of using drones as compared to helicopters is that they are less costly than operating a full-sized helicopter.

One limitation of drones is operating them Beyond the Visual Line Of Sight. In the EU, it is not allowed to fly drones beyond that point as there are air-traffic and safety concerns related to people and infrastructure. However, there are currently attempts to develop a system that will allow autonomous drones to be flown.

2. Aircraft

Another option is to attach sniffers to aircrafts such as planes or helicopters.

What are the dis-/advantages?

As to advantages, aerial surveillance can aid in targeting offenders at sea which can then be required to give a fuel sample while in the port. A helicopter is an efficient tool for this purpose, because it can cover large areas and many ships in a speedy manner. Compared to drones, the advantage of using a helicopter is that it has a much larger operational capacity.

However, as mentioned previously, operating costs are higher when compared to drones. Additionally, the localization of the exhaust plume can be difficult, even with software models and an experienced aircrew, which can result in several attempts being required before a successful measurement can be made.

3. Fixed land-based sniffers

Another solution to monitoring ship emissions are fixed land-based measuring stations/sniffers, which can be fitted on port entrances or bridges, and can analyse the drifting plumes of ships passing through.

What are the dis-/advantages?

Operational costs can be lower than with aircraft as these do not require a pilot or fuel to run.

As opposed to drones, land-based sniffers are unable to get close to the ship itself and thus obtain a good reading of the exhaust gasses. Additionally, this method only covers a limited area compared to drones and aircraft.

4. Optical remote sensing

There is another method for measuring emissions that is not as widely used in the marine industry as the ones described above. Optical Remote Sensing uses the absorption of sunlight to identify specific gases from a longer distance.

What are dis-/advantages?

One advantage of this method is that it can be used from a long distance, which could potentially cut operational costs in comparison to drones or aircraft.

The main disadvantage is that while this method can measure NO2 and SO2, it still cannot accurately measure CO2 which limits its usability. Further, this method requires further assumptions about the engine load and operational mode of the ship to calculate the sulphur content of the fuel being used.


The use of sniffers is still at the beginning stage and raises some difficulties. As they need to be exposed to the ships’ exhaust plume, the method usually relies on weather conditions to enable the detection of individual exhaust plumes and their monitoring. However, there is room for further development of remote sensing technologies, which can lead to more cost-effective solutions. Overall, the use of sniffers in either airborne surveillance or land-based settings is becoming increasingly popular.