In comparison to some cities, air quality in Christchurch, New Zealand, is relatively good. However, with a population of just under 400,000 and a thriving economy in normal times, air pollution, due to volatile organic compounds (VOCs), is present at detectable concentrations. 

Then, in 2020, came the coronavirus pandemic. 

 On 25 March 2020, New Zealand entered a government mandated Level 4 lockdown in response to the COVID-19 emergency. 

In accordance with these measures, Syft Technologies closed its doors and its staff members joined the rest of Christchurch’s citizens in isolation. 

What impact did the different lockdown levels have on Syft: 
Level 4Full lockdown, with only essential services allowed to operate from business premises.
Level 3Limited staff allowed on-site, working in separate am and pm shifts. 
Level 2Most staff back in the office, while maintaining social distancing and increased cleaning protocols. 

Businesses were given a few days’ notice to prepare for the lockdown and during this timeSyft’s Science and Applications Teams jumped into action upon the realization that the lockdown presented a unique opportunity to track the concentrations of VOCs in outdoor air throughout this period of tightly restricted economic activity. 

Late on the eve of the lockdown, Dr Yadong Wang, Dr Kalib Bell and Dr Ian Farrellalong with some of our ever-helpful Production Engineers, Jozef Knottenbelt and Matt Lynn, got preparations underway to start taking direct, real-time measurements of VOCs in the outdoor air every 10 minutes with a Voice200ultra Selected Ion Flow Tube-Mass Spectrometer (SIFT-MS), until the country re-opened.  

The Voice200ultra was housed at Syft’s headquarters, in an industrial area of Christchurch, and outdoor air samples were delivered to the instrument by a pump. The instrument was set up to operate unattended and continuously for 10 weeks, capturing the chemical signature of the city’s new rhythm. Wind speed has a significant influence on air pollution, so wind speed was also logged continuously based on the local weather data obtained from Weather Underground. The Voice200ultra is an inherently stable instrument and was made more so, by running an automated validation proceduredaily. 

Because they had no idea what changes would occur, Yadong and Kalib set up the Voice200ultra to operate in an untargeted scan mode, recording data on all species produced from the air samples, over the mass range 15 to 200 m/z. 

New Zealand remained at alert Level 4 from March 25th until April 27th when, in response to an improving situation, the alert level was reduced to Level 3, with a partial lifting of restrictions. Then on May 13th the alert level was reduced to Level 2. Finally, on June 8th the alert level was dropped to Level 1, removing all restrictions except border controls. 

Throughout this extraordinary time, the Voice200ultra kept making continuous measurements six times an hourrecording the effect of the various stages of lockdown on VOC concentrations in the city’s air. Every day, Yadong would diligently connect remotely to the instrument from home, to check how it was getting on. 

What did they find? 

By the middle of June, with city life returning to normal, it was time for Yadong to compile the data and see what conclusions could be drawn. 

Data was extracted for a suite of compounds that commonly figure in air pollution studies (formaldehyde, acetaldehyde, beta-pinene, acetone, ethanol, toluene, acrolein, xylenes+ethylbenzene). 

The charts to the right picture what they found. The red dotted line shows the wind speed, the solid colored lines show individual compounds. 

In Figure 1 (a), we see the concentrations of all VOCs remain low and stable during Level 4 lockdown.  

As the lockdown moved into Level 3, local business gradually restarted. Figure 1 (b) shows the dynamics of VOC concentrations during Level 3 Lockdown. The averaged local ethanol and toluene concentrations varied significantly compared to the stable dynamics observed in Level 4 (these two compounds are a good indicator of industry and traffic emissions). 

Including information on local wind speed to the dataset, we found high concentrations normally correspond to lower local wind speeds. 

The overall ethanol concentration increased further as most businesses got back on track in Level 2. Furthermore, we saw ethanol concentrations start to rise in the morning around 10am, and slowly decay during the afternoon – see Figure 1 (c).  

Figure 1. Continuous real-time monitoring of VOC concentrations during New Zealand COVID lockdown Level (a) 4, (b) 3 and (c) 2, in comparison with local wind speeds (red dashed line). 

If you are wondering how concentrations vary throughout the day during the different stages of lockdown, take a look at Figure 2, which tracks toluene concentrations throughout three different days during the lockdown March 31st 2020 (Level 4), May 6th (Level 3) and May 19th (Level 2).

You will notice that during lockdown Level 4 (blue line), the toluene concentration was steady at a low level of 0.2 ppb. 

 When the country switched to lockdown Level 3 (red line), Syft’s Production team began working two shifts per day starting at 6am and 2pm. You can see the toluene concentration begins to rise around 6 am. In addition, the concentration of toluene climbs slightly, during the shift rotation around 1:30 pm. 

In lockdown Level 2 (green line), most nearby companies were back to normal business hours, and we see a corresponding increase in the toluene concentration in the morning, around 8 am. 

This simple experiment shows how SIFT-MS can generate informative real-time measurements of a range of volatile organics, including some – formaldehyde and acrolein, for example – that are tricky to measure directly with other analytical technologies. 

Figure 2. Variations in toluene concentration throughout the day, at different lockdown levels. 

Banner image from left to right: Matt Lynn (Production), Dr Ian Farrell (R&D), Dr Yadong Wang (R&D), Dr Kalib Bell (R&D) and Jozef Knottenbelt (Production), who were instrumental in getting this experiment underway. With thanks to Thomas McKellar.

If you are interested in using SIFT-MS for the measurement of VOCs in air, email us on or visit the contact page of our website.