Ozone (O3) in Buildings
•
•
•
•
Sources
Fate
Effects
Measurement
Ozone (O3)
• Stratospheric good
• Tropospheric bad (formation)
• Standards / Regulations
• Relative exposure analysis (include I/O)
Exposure (I / O)

C in t in Bin
C outt outB out

 C in  t in  Bin 




C
t
B
 out  out  out 
Exposure (I/O) ≈ (0.2 – 0.7) x 18 x 0.4 = 1.4 – 5
Health Effects
• Effects well understood (40+ years of research)
• Inflammation of respiratory tissue
• Irritation, coughing, pain upon deep breathing
• Trische et al. (2006) – infants w/ mothers w/ asthma
• Bell et al. (2006) – strong link to premature mortality
Sources of Ozone
• Outdoor air
• typical source in urban area (summer) = 2 – 20 mg/hr
• Laser printers
• Photocopy machines
• Electrostatic precipitators
• Explicit ozone generators (100s – 1000s mg/hr)
• Ion generators
Ion Generators
• Enormously popular (M sold annually; > 1% homes)
• Heavily marketed
• Incidental O3 formation
• less than explicit O3 generators
• Claims often vague (arguably deceiving)
• Comparatively ineffective
• Often marketed with children in ad
Indoor Reactions
Ozone Removal and By-Products
Ozone
NO
O3
R
R
R R
R R
R
BDB
R R
PR
R
R
R
NO3
NO2
VOCs
stuff


dC
V
 minj  Q   vd,j Aj  C
dt
j


Discussion of Practical area integrated deposition
Heterogeneous Reactions
Homogeneous Reactions
Ozone + C=C
Ozone + specific VOCs (C=C)
“bad stuff”
Reactions in air AND on materials
Examples of C=C
–
–
–
–
–
–
–
–
–
Styrene
d-Limonene
α/β-Pinene
Myrcene
α-Terpinene
Citronellol
Geraniol
Linalool alcohol
α-Terpineol
Some Important Sources
• Carpet (e.g., styrene)
• Cleaning products
• Polishes and waxes
• Air fresheners
• Other scented consumer products
• Wood / plants
Potential Effects
• Odors
• some aldehydes < 50 ppt; carboxylic acids to low ppb
• Contact allergens (e.g., limonene oxidation products)
Nilsson et al., Chromatographia, 42: 199-205 (1996)
• Eye irritants (e.g., formaldehyde, acrolein)
• terpene/ozone oxidation products
Kleno and Wolkoff, Intl’ Arch Occup. Environ. Health, 77: 235-243 (2004).
• Airway irritants
• terpene/ozone oxidation products (HCHO, acrolein, …….)
• 33% reduction in mean respiratory rate of mice (30 min)
Wolkoff and Neilsen, Atmospheric Environment, 35: 4407-4417 (2001); Wolkoff et al., Indoor
Air, 10: 82-91 (2000); Clausen et al., Environment International, 26: 511-522 (2001)
• Tox info not available for most oxidation products (!!)
Example: Solid Air Freshener
1,000,000.0
0.02-0.1
100,000.0
10,000.0
0.2-0.3
3
PART ICL E S [# /cm
]
0.1-0.2
1,000.0
0.3-0.4
100.0
0.4-0.5
10.0
0.5-0.7
1.0
0.1
-50
50
150
250
350
450
550
650
750
TIME [min]
Sarwar et al., Journal of the Air & Waste Management Association, 54: 367-377 (2004)
Chamber Experiment w/ Perfume
PM
1,000,000.0
O3
+
0.02-0.1
10,000.0
3
PA R T I C L E S [#/cm
]
100,000.0
0.1-0.2
1,000.0
0.2-0.3
100.0
0.3-0.4
10.0
0.4-0.5
1.0
0.5-0.7
0.1
-50
0
50
100
150
200
TIM E [min]
250
300
350
Measurements
• Personal
• diffusion-based (calculation in lecture)
• Ambient
• UV-absorbance
http://www.ogawausa.com/passive.html
• 2B-Technologies
• schematics (single and dual cell)
• specifications
http://www.twobtech.com/
Passive Ozone Samplers
http://www.ogawausa.com/passive.html
UV Absorbance
Summary
• Ozone inside of buildings is important
– even if lower concentrations indoors
– outdoor ozone breathed indoors to a great extent
• Ozone + Reaction Products both health issues
• Important to be able to predict indoor ozone levels
• Important to be able to measure indoor ozone
• Measurement technologies dramatically improved
– cost, size (mobility)
VOCs in Buildings
•
•
•
•
Sources
Fate
Effects
Measurement
Volatile Organic Compounds (VOCs)
VOC
• What is a VOC?
–
–
–
–
Organic = C, H
“affinity for gas phase”, “significant” evaporation rate
Tb < 260 oC
Thousands (reduce list to 50 to 100)
• What is TVOC?
Categories
• Odor-causing
• Irritating
• SBS – fatigue, eyes, headaches, upper resp., etc
• Other – skin irritation, asthma, MCS
• Toxic/Hazardous
• Carcinogen
• Teratogen
• Neurotoxin, etc.
• Reactive
• Generally w/ ozone
Representative Examples
•
•
•
•
•
•
•
•
•
•
•
•
Benzene
Toluene
BTEX
Ethylbenzene
Xylenes (all isomers)
Trimethylbenzenes (all isomers)
Dichlorobenzenes (not all isomers created equal)
Tetrachloroethene (PERC)
Chloroform (a THM)
4-Phenylcyclohexene (4-PCH)
Styrene
Terpenes (limonene, pinene, etc.)
Formaldehyde (HCHO) – often not classified as a VOC
Relative Exposure to VOCs
C in t in Bin
Exposure (I / O) 
C outt outBout
 C in  t in  Bin 
 



 C out  t out  Bout 
Exposure (I/O) = 3 x 18 x 0.4 = 22
indoor contribution > 95% (most volatile HAPs, etc.)
Some Important Sources
•
•
•
•
•
•
Building materials and furnishing (wood, adhesives, gyp board)
Flooring materials (carpet, vinyl flooring, wood)
Architectural coatings (paints, varnishes, waxes, etc.)
Consumer products (cleaners, detergents, fresheners, personal, etc.)
Combustion sources (ETS, candles, gas stoves, space heaters)
Electronics (computers, photocopiers, printers, TVs/VCRs)
•
•
•
•
•
Heating of particulate matter
Soil vapor intrusion
Drinking water
Mold (MVOCs)
People
Measurement Issues
Objective(s)
Required detection limits
(Real-time) vs. (collect and analyze)
Non-specific vs. species specific (speciated)
Grab versus integrated
Interferences
Preservation requirements
Quality assurance requirements
EPA/OSHA/NIOSH methods exist?
Cost/Budget
Measurement Method
•
•
•
•
•
•
•
•
•
•
Sample Collection Methods
• Real-time (field) measurement/analysis
– generally = sensor (mostly FID, PID)
– some = separation (w/ GC) + sensor
– Also – colorimetric tubes (general: MDL > 1 ppm)
• Collect for analysis
– whole-volume samplers (canisters, bags)
– concentration samplers (sorbents, SPME)
– either case = preservation and analysis in laboratory
Canisters
• Whole volume
• Grab versus integrated
• EPA Methods TO-14 / 15
• Benefits
• Inert/impermeable
• Experience
• Multiple analyses
1 – 15 L
• Drawbacks
• bulky
• cleaning
• Scratch
• Ozone / Sample stability
http://www.skcinc.com
400 mL
Tedlar Bags
•
•
•
•
•
Whole volume
Tedlar = polyvinylfluoride
Pump to collect (unlike cans)
Issues:
Benefits:
–
–
–
–
inert / impervious (like cans)
repeat samples (like cans)
lighter than cans
lower initial cost than cans
• Drawbacks
–
–
–
–
not as reuseable as cans
tearing
cleaning
stability with some compounds
http://www.essvial.com/products/airsample.html
0.5 – 100 L
Sorbent Sampling
• VOC adsorbs to solid adsorbent
• Passive sampling
– Similar to ozone badge w/o reaction
– Integrated sample over 24 hours, etc.
– Indoor, personal, outdoor
http://www.aerotechpk.com/
• Active Sampling
–
–
–
–
–
Pump through packed tube
Collect mass over known volume
C = m/V
Short-term vs. integrated
More control, but more difficult
http://www.sisweb.com/index/referenc/resin10.htm
Sorbent Tubes
• EPA Method TO-17 = TD/GC/MS (important)
• Various sorbents can be used
•TO-17 page 33
• Note VOC types/ranges
• Some issues
• Method detection limit, precision, accuracy (pg. 28/29)
• Sample preservation
• Breakthrough volume (see next slide)
• Artifact formation (especially via ozone)
• Sorbent pre-conditioning / breakdown over time
• Use of multi-sorbent beds
• Focus on Tenax-TA
Tenax-TA
• 2,6-diphenylene oxide polymer resin (porous)
• Specific area = 35 m2/g
• Pore size = 200 nm (average)
• Density = 0.25 g/cm3
• Various mesh sizes (e.g., 60/80)
• Low affinity for water (good for high RH)
• Non-polar VOCs (Tb > 100 oC); polar (Tb > 150 oC)
• lighter polar – Carbotrap and Carbopack-B common
• Artifacts w/ O3: benzaldehyde, phenol, acetophenone
Solid-Phase Micro-Extraction
• Short inside-out GC column
• Coated fiber (extracting phase):
– PDMS / DVB / Carboxen
• Benefits
–
–
–
–
–
–
Highly concentrating for many indoor VOCs (ppt levels)
Reusable
Relatively low cost
Small / light weight
Possible use in other media
Ease of injection to GC
• Drawbacks
– Less experience / acceptability
– Preservation issues
– Difficulties w/ calibration – work-up
Gas Chromatography (GC)
• Goal = separate compounds
• Use capillary column
• Properties of column
• Properties of chemical
• Thermal program of GC oven
• Temporal passage to a detector
• analyze “peaks”
• analyze molecular fragments (MS)
Gas Chromatography (GC)
http://www.chromatography-online.org/GC/Modern-GC/rs2.html
Figure 5: Chromatogram of Tenax-sampling in a show case (sample
volume 1l) - iaq.dk/iap/iaq2003/posters/hahn5.gif
Blue slides = www.sisweb.com/art/referenc/aap54
GC Issues
• Type of injection?
• Need to cryofocus?
• Type of column?
• Type of detector?
– If MS, model of detection
• Temperature programs
• Instrument calibration / response
Detectors
• Flame ionization detector (FID)
• Photoionization detector (PID)
Non-specific or
speciated (w/ GC)
• Electron capture detector (ECD)
• Mass spectrometer (MS)
w/ speciated (w/ GC)
• These are primary detectors for VOCs in indoor air
• Specific uses vary considerably
Flame Ionization Detectors (FID)
•
•
•
•
•
Relatively simple system 
Ions formed – migrate to plate
Generate current
Detection – typical to pg/s
Benefits
– Rugged, low cost, workhorse
– Linear response over wide range
– Insensitive to H2O, CO2, SO2, CO, NOx ..
• Drawbacks
– No identification
– Lower response if not simple HC
– Destructive
www.chem.agilent.com
Photoionization Detectors (PID)
•
•
•
•
UV light ionizes VOCs --- R + hv  R+ + eCollected by electrodes = current
VOCs with different ionization potentials
Benefits
– Simple to use
– Sample non-destructive (relatively)
• Drawbacks
–
–
–
–
No identification
Highly variable responses
Not all VOCs detected
Lamp burnout / contamination
http://www.chemistry.adelaide.edu.au/external/soc-rel/content/pid.htm
Electron Capture Detectors (ECD)
• Low energy Beta emitter = 63Ni
• e- attracted to positively charged electrode (anode)
• Molecules in sample absorb e- and reduce current
– effective: halogens (recall SF6), nitrogen-containing
• Benefits
– 10-1,000 x more sensitive than FID
– femtogram/s ----- ppt levels
• Drawbacks
–
–
–
–
More limited linear range than FID
Radiological safety requirements
http://www.chemistry.adelaide.edu.au/exte
O2 contamination issues
rnal/soc-rel/content/ecd.htm
Response strong function of T, P, flowrate
Mass Spectrometer (MS)
• Bombard molecules w/ intense electron source
• Generate positive ion fragments
• Use fragment fingerprint to identify molecule
• Quantify amount of fragments to determine mass
• Most common MS = quadrupole
Quadrupole MS
• Electron source
• Four rods (electromagnets)
–
–
–
–
–
•
•
•
•
Applied Voltage
DC/AC components
Voltages = fn(time)
Affects trajectory
Selective M/Z to detector
Cycles different M/Z
Yields mass spectrum
Always same for a molecule
System in vacuum
http://www.chemistry.adelaide.edu.au/exter
nal/soc-rel/content/quadrupo.htm
Total Ion Chromatogram (TIC)
linalool
limonene
Mondello et al., J. of Chromatography A, 1067: 235-243 (2005)
Mass Spectrum
Example mass spectrum (fingerprint)
Mass Spectrometer
• Benefits
– “Gold standard”
– Amount AND identification of unknowns
• Drawbacks
– Cost
– Complexity
– Maintenance
Summary
• VOCs important in indoor environments
• Many types of VOCs
– Different properties
– Different effects
– Different sample collection and analysis protocols
• Sampling and analysis protocols NOT TRIVIAL
– Many types of collection methods
– Many types of analysis methods / including detectors
– A lot of issues involved w/ sample/analysis decisions
– A lot can go wrong (difficult business)
– Cumbersome and costly -------- but really important