Indoor chemistry: Indoor chemistry: Materials, Ventilation Materials, Ventilation Systems and Occupant Systems and Occupant activitiesactivities

G.C.Morrison*, R.L. Corsi, H. Destaillets, W.W. G.C.Morrison*, R.L. Corsi, H. Destaillets, W.W. Nazaroff and J.R. WellsNazaroff and J.R. Wells

*Assistant professor of Civil, Architectural and *Assistant professor of Civil, Architectural and Environmental EngineeringEnvironmental EngineeringUniversity of Missouri-RollaUniversity of Missouri-Rolla

Indoor environmentsIndoor environments

Complex indoor exposuresComplex indoor exposures

• Furnishings (e.g. vinyl floor)• Emissions increase exposure

• formaldehyde, VOCs, SVOCs• ventilation dilutes• more fresh air = lower exposure

• ventilation brings in • outdoor pollutants

• transformative chemistry • alters existing compounds•increases occupant exposure

Focus here: ozone Focus here: ozone chemistry and choiceschemistry and choices Smog ozone carries reactive Smog ozone carries reactive

potential into buildingspotential into buildings ReactionsReactions

– Remove ozoneRemove ozone– Produce reaction productsProduce reaction products

ozonealdehydesacidsperoxidesfree radicals…

polluted outdoor air

indoor surfaces

indoor gases

Stakeholders and Stakeholders and controlscontrols

1.1. Building materials Building materials and constructionand construction

2.2. Building Building management: HVAC, management: HVAC, cleaning, renovationcleaning, renovation

3.3. Occupant Occupant activitiesactivities

3

1

2

Building Materials and Building Materials and ozone surface ozone surface chemistrychemistry Painted wallsPainted walls

– Poor ozone sinkPoor ozone sink– Generates some formaldehyde newGenerates some formaldehyde new– little reactivity when agedlittle reactivity when aged

CarpetCarpet– Good ozone sinkGood ozone sink– Generates aldehydes with high yield when newGenerates aldehydes with high yield when new– lower yield when agedlower yield when aged

Other surfacesOther surfaces– Vinyl: little reactivityVinyl: little reactivity– Brick and concrete: good ozone sinksBrick and concrete: good ozone sinks– Linoleum: medium sink, some aldehydesLinoleum: medium sink, some aldehydes

Building materials Building materials and gas-phase and gas-phase chemistrychemistry Wood products, Wood products,

natural paintsnatural paints– Release Release

“terpenes” that “terpenes” that react with react with ozoneozone

reactive speciesand intermediates

aldehydes andketones

acids andcarbonyl-acids

more volatile

less volatile(generatesSOAs)

hydroxylradical (0.81)

hydrogen peroxideHOOH

OH

OOHperoxy radical

alkoxy radicalRO

alkyl peroxy radicalROO

OO

O

-pinene ozonide

formaldehyde (0.18)O CH2

O O

pinonaldehyde (0.51)

O

acetone (0.06) formic acid (0.1)

OH

O

norpinonic acid (0.043)

HO

O

O

HOO

O

pinalic acid (0.045)

pinic acid (0.03)OH

O

OH

O

+ O3

-pinene

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

-80 -60 -40 -20 0

ozone increment (ppb)

form

ald

ehyd

e in

crem

ent

(pp

b)

Building materials Building materials comparison: formaldehyde comparison: formaldehyde vs ozone incrementsvs ozone increments

better

worsenew latex paint

new carpet

brick

unsealed wood (-pinene)

glass

unpainteddrywall

concrete

old carpet old paint

sealed wood (-pinene)

vinyl floor

indoor air quality modelsteady-state, 100 ppb O3 air-exchange rate = 0.5 h-1

building volume = 250 m3

Building management Building management and ozone chemistryand ozone chemistry HVAC systemsHVAC systems

– DuctsDucts poor to moderate ozone sinkspoor to moderate ozone sinks duct liners can generate aldehydesduct liners can generate aldehydes

– New filtersNew filters poor ozone sinks, some formaldehyde poor ozone sinks, some formaldehyde

when newwhen new

– Soiled filtersSoiled filters Excellent ozone sinks, high aldehyde Excellent ozone sinks, high aldehyde

yieldsyields

Building management: Building management: formaldehyde increment formaldehyde increment vs ozone incrementvs ozone increment

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

-70 -60 -50 -40 -30 -20 -10 0

ozone increment (ppb)

form

ald

ehyd

e in

crem

ent

(pp

b)

soiled filter, HVAC with no recirculation

soiled filter, HVAC with 50% recirculation

steel ductduct liner

new filter

better

worse

Occupant activities Occupant activities and ozone chemistryand ozone chemistry Use of fragrance and cleaning productsUse of fragrance and cleaning products

– Ozone removal or product formation depends on Ozone removal or product formation depends on formulationformulation

– Limonene: good ozone sink, Limonene: good ozone sink, -pinene: good ozone sink, formaldehyde-pinene: good ozone sink, formaldehyde– Not discussed: irritants, aerosols!Not discussed: irritants, aerosols!

Use of soaps and cooking oilsUse of soaps and cooking oils– Surfaces become good sinks for ozoneSurfaces become good sinks for ozone– Formaldehyde yield uncertain, many other Formaldehyde yield uncertain, many other

aldehydesaldehydes Tobacco smokeTobacco smoke

– Ozone react with styrene, isoprene, limonene, …Ozone react with styrene, isoprene, limonene, …– Products include formaldehyde, other aldehydesProducts include formaldehyde, other aldehydes– Nicotine reacts with ozone on surfacesNicotine reacts with ozone on surfaces

0.0

5.0

10.0

15.0

20.0

25.0

30.0

-100 -80 -60 -40 -20 0

ozone increment (ppb)

form

ald

ehyd

e in

crem

ent

(pp

b)

Occupant activities: Occupant activities: formaldehyde vs ozone formaldehyde vs ozone incrementincrement

smoking

cleaning, myrcene

cleaning, limonene

cleaning, -pinene

cleaning, -pinene

soiled counterbetter

worse

ConclusionsConclusions

Formaldehyde-ozone tradeoffFormaldehyde-ozone tradeoff– Building materialsBuilding materials

good: brick, concrete, bare drywall good: brick, concrete, bare drywall air out wood, carpetair out wood, carpet

– Building managementBuilding management filter replacement? Not clearfilter replacement? Not clear

– Occupant activitiesOccupant activities Cleaning products without Cleaning products without -pinene-pinene Less cleaning = lower ozone consumption?Less cleaning = lower ozone consumption?

Just scratched the surfaceJust scratched the surface– Other reaction productsOther reaction products– Other metrics of toxicity or irritancyOther metrics of toxicity or irritancy

Indoor ChemistryIndoor Chemistry

HETEROGENOUS (surface) CHEMISTRY

─ oxidation ├ O3 + ├ ·OH + └ NO3 +

┬ oxidation │ └ O2 + lipids (oils) └ hydrolysis └ H2O + resins, plasticizers, flame retardants

terpenes and other VOCs

HOMOGENOUSCHEMISTRY

┬ oxidation │ │ lipids (oils, soaps, skin oils) │ └ O3 + terpenes │ nicotine └ acid-base │ nicotine └ H+ + trimethylamine

Condensed-phase chemistry

Gas-phase chemistry

chemistry takes place at surfaces