IAQM Indoor Air Quality conference 2020 Outdoor Indoor Air Quality Interactions: Current Issues

1. Part of the BRE Trust
IAQ monitoring – equipment and protocols
Stuart Upton, BRE
IAQM Indoor Air Conference
22 June 2020
© BRE

2. Presentation overview
1. Examples of monitoring equipment
• Gases and particles
• ‘Traditional’ and more recent
equipment/sensors
2. Selection considerations
• Why are you monitoring?
• Equipment characteristics and limitations
3. Possible siting
• Outdoor/Indoor
• Indoor
4. Data, communication and pitfalls

3. Equipment: Gases (1: Traditional analysers)
Large traditional analysers, e.g.:
• NOx (Chemiluminescent)
• Ozone (UV absorption)
• CO (IR absorption)
– Work well at ‘environmental’ concentrations
(ppb) and/or for longer-term monitoring.
– Wide range of certifications, approvals,
Reference Methods
– Large, not very portable, mains electricity
supply required.
© BRE, 2011

4. Equipment: Gases (2: Portable/modern sensors)
Portable/fixed instruments/sensors available for a wide range of
gases, vapours.
• Many work less well at ‘environmental’
(ppb) concentrations for gases/vapours.
• Often used for short-term monitoring, but
can be used for longer-term monitoring
also.
• Very portable, often both battery and
mains electricity power options
© BRE, 2011

5. Equipment: Particle monitoring
Wide range of equipment – wide range of particle sizes (1nm to 15 µm).
© BRE, 2011
Variety of instruments and measurement techniques – for
outdoors/indoors, portable or ‘fixed’
§ Mass (e.g. TEOM) fitted with pre-separators/inlets to give specific particle mass
fractions (e.g. PM10, PM2.5)
§ Light scattering (note: this technique can only detect particles between ~0.3 to
10µm) gives a calculated mass concentration based on assumed density, shape
etc.)
§ Other methods: ß-attenuation, obscuration, gravimetric
§ Sub-micron particles: condensation nucleus counting, charge/electrical mobility

6. General considerations for monitoring
1. Why are you doing it?
• Pre-occupation certification compliance e.g. (BREEAM, WELL, LEED)
• Post-occupancy evaluation
• Trouble-shooting: if problems arise or occupant reassurance needed
2. What are you monitoring?
• Which pollutants do you need to measure?
• What are the likely concentrations?
• Comfort parameters (generally T & RH)
• Don’t forget ventilation (indoor concentrations are source term and
ventilation rate dependent!)
3. Monitoring period required?
• Short- or long-term?
• Single survey visit (‘snap shot’ of conditions on one day only – will it be
representative?) or installing equipment for a longer period?
• Continuously logged or time-averaged?
• Maximum or mean concentrations required?

7. Monitoring equipment – selection considerations
• Buy or hire? (More limited range of equipment available for hire)
• What is your budget – as costs of equipment vary greatly?
• The number of monitoring locations required
• Can you move equipment between locations if needed?
• Multiple low-cost sensors or multi-point sampling to reference method (gases
only)
• Low cost sensors improving all the time. Multiple sensor use gives greater
confidence in data obtained. Single low-cost sensor – less confidence.
• If measurements are required to demonstrate compliance with health or
environmental legislation then a reference method or ‘traceable’
measurement may be required.
• Understanding of pollutant behaviour and equipment characteristics
• Ozone and NOx (if measuring ozone, need to understand NO also)
• Cross-sensitivity of sensors, e.g. other compounds that can be ‘detected’ instead
(e.g. UV or IR absorption)
• ‘Derived’ pollutant concentrations (using algorithms to predict concentrations of a
pollutant from measurements of other pollutants).

8. How and where to site monitoring equipment? (1)
Outdoors (outdoor reference usually required for building IAQ)
• Away from local pollution sources (as much as possible)
• Near to ventilation inlets
• For ‘spot’ measurements, suggest before (and also after if possible) any indoor
measurements. Measuring beforehand gives you the quality of the air that will
be ventilating into the building during your indoor measurements!
Indoor : Outdoors
• Pairs of measurements as near ‘across the façade’ as you can reasonably get
– to avoid any potential indoor source interference.
Indoors
• In areas where most staff are based, i.e. the areas most commonly used.
• Away from doors, openable windows, air supply vents and grilles (minimum
distance of 1 metre, although >2 metres is preferred if possible).
• Between incoming ventilation air supply points and the centre of the
area/room.

9. How and where to site monitoring equipment?(2)
Indoors (continued)
• In areas with unobstructed airflows and pathways for free flow of air to sensors.
• Away from the immediate breathing zones of any occupant (minimum distance of
1 metre, although >2 metres is preferred if possible).
• Away from any fans, heaters or localised sources of pollutants such as copiers,
printers, kettles, cooking facilities, etc.
• At a height above the floor of between approximately 1.2 to 1.6 metres (i.e.
within the normal breathing height of occupants, either seated or standing).
• To typically monitor an area of up to a maximum of approximately 100 to 150 m2
only.
• Don’t place the monitors in direct sunlight or too close to heaters/radiators.

10. Data and communication
How will you store data and/or communicate/download it?
• Do not underestimate this!
• ‘Oh yes, but these days we have the:
• Internet-of-things, wi-fi, the ‘Cloud’, Bluetooth, ‘Plug and Play’ etc etc’.
Some areas (even in cities) have:
• Poor signal coverage
• Poor signal coverage for certain networks – worth checking!
Very many buildings have:
• Poor wi-fi provision/coverage in some/many areas
• Some building structures (metal or the type of concrete) have very
poor internal (and external) signal transmission capabilities
Internal data storage - as a ‘physical download’ back-up option is still
very useful!
Long-term data storage? May be needed years later for subsequent
health/insurance claims.

11. Other potential pitfalls!
Obviously, all equipment requires proper, current calibration.
However, be very careful with ‘auto-calibration’ features – especially
common with carbon dioxide (CO2) monitoring instruments.
These are effectively ‘local area background resets’ rather than
calibrations. They assume that, at some point over a period (e.g. 2
weeks) the concentration of CO2 will have decreased to approximately
the current outdoor background of ~400ppm.
However, if the concentration hasn’t decreased to that level within the
period – the instrument may assume that it has and reset to this level
thus introducing a reading off-set!
Can be a problem if you are trying to monitor in a permanently-occupied
space or somewhere with higher background CO2 concentrations.

12. – Homes, schools, offices, hospitals, aircraft cabins,
narrowboats etc etc!
It is possible to monitor in all types of location!

13. Thank you for your attention!
BRE Contact for further information:
Stuart Upton
BRE
E-mail: stuart.upton@bregroup.com
Telephone: +44 (0) 1923 664479
Website: www.bre.co.uk