Indoor chemistry: Materials, Ventilation Systems and Occupant activities G.C.Morrison*, R.L. Corsi, H. Destaillets, W.W. Nazaroff and J.R. Wells *Assistant professor of Civil, Architectural and Environmental Engineering University of Missouri-Rolla

Indoor environments Complex indoor exposures Complex 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 chemistry and choices Smog ozone carries reactive potential into buildings Smog ozone carries reactive potential into buildings Reactions Reactions –Remove ozone –Produce reaction products ozone aldehydes acids peroxides free radicals … polluted outdoor air indoor surfaces indoor gases

Stakeholders and controls 1. Building materials and construction 2. Building management: HVAC, cleaning, renovation 3. Occupant activities 3 1 2

Building Materials and ozone surface chemistry Painted walls Painted walls –Poor ozone sink –Generates some formaldehyde new –little reactivity when aged Carpet Carpet –Good ozone sink –Generates aldehydes with high yield when new –lower yield when aged Other surfaces Other surfaces –Vinyl: little reactivity –Brick and concrete: good ozone sinks –Linoleum: medium sink, some aldehydes

Building materials and gas-phase chemistry Wood products, natural paints Wood products, natural paints –Release “terpenes” that react with ozone

Building materials comparison: formaldehyde vs ozone increments better worse new latex paint new carpet brick unsealed wood (  -pinene) glass unpainted drywall concrete old carpet old paint sealed wood (  -pinene) vinyl floor indoor air quality model steady-state, 100 ppb O 3 air-exchange rate = 0.5 h -1 building volume = 250 m 3

Building management and ozone chemistry HVAC systems HVAC systems –Ducts poor to moderate ozone sinks poor to moderate ozone sinks duct liners can generate aldehydes duct liners can generate aldehydes –New filters poor ozone sinks, some formaldehyde when new poor ozone sinks, some formaldehyde when new –Soiled filters Excellent ozone sinks, high aldehyde yields Excellent ozone sinks, high aldehyde yields

Building management: formaldehyde increment vs ozone increment soiled filter, HVAC with no recirculation soiled filter, HVAC with 50% recirculation steel duct duct liner new filter better worse

Occupant activities and ozone chemistry Use of fragrance and cleaning products Use of fragrance and cleaning products –Ozone removal or product formation depends on formulation –Limonene: good ozone sink, –  -pinene: good ozone sink, formaldehyde –Not discussed: irritants, aerosols! Use of soaps and cooking oils Use of soaps and cooking oils –Surfaces become good sinks for ozone –Formaldehyde yield uncertain, many other aldehydes Tobacco smoke Tobacco smoke –Ozone react with styrene, isoprene, limonene, … –Products include formaldehyde, other aldehydes –Nicotine reacts with ozone on surfaces

Occupant activities: formaldehyde vs ozone increment smoking cleaning, myrcene cleaning, limonene cleaning,  -pinene cleaning,  -pinene soiled counter better worse

Conclusions Formaldehyde-ozone tradeoff Formaldehyde-ozone tradeoff –Building materials good: brick, concrete, bare drywall good: brick, concrete, bare drywall air out wood, carpet air out wood, carpet –Building management filter replacement? Not clear filter replacement? Not clear –Occupant activities Cleaning products without  -pinene Cleaning products without  -pinene Less cleaning = lower ozone consumption? Less cleaning = lower ozone consumption? Just scratched the surface Just scratched the surface –Other reaction products –Other metrics of toxicity or irritancy

Indoor Chemistry HETEROGENOUS (surface) CHEMISTRY ─ oxidation ├ O 3 + ├ ·OH + └ NO 3 + ┬ oxidation │ └ O 2 + lipids (oils) └ hydrolysis └ H 2 O + resins, plasticizers, flame retardants terpenes and other VOCs HOMOGENOUS CHEMISTRY ┬ oxidation │ │ lipids (oils, soaps, skin oils) │ └ O 3 + terpenes │ nicotine └ acid-base │ nicotine └ H + + trimethylamine Condensed-phase chemistry Gas-phase chemistry chemistry takes place at surfaces