Indoor chemistry: Materials, Ventilation Systems and Occupant activities

1. 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

2. Indoor environments • 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

3. Focus here: ozone chemistry and choices • Smog ozone carries reactive potential into buildings • Reactions • Remove ozone • Produce reaction products indoor gases aldehydes acids peroxides free radicals … ozone polluted outdoor air indoor surfaces

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

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

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

7. Building materials comparison: formaldehyde vs ozone increments indoor air quality model steady-state, 100 ppb O3 air-exchange rate = 0.5 h-1 building volume = 250 m3 new latex paint worse unsealed wood (a-pinene) new carpet better sealed wood (a-pinene) concrete brick glass old paint vinyl floor old carpet unpainted drywall

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

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

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

11. Occupant activities: formaldehyde vs ozone increment smoking worse cleaning, myrcene cleaning, b-pinene cleaning, limonene cleaning, a-pinene better soiled counter

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

13. HOMOGENOUS CHEMISTRY HETEROGENOUS (surface) CHEMISTRY Gas-phase chemistry ─ oxidation ├ O3 + ├ ·OH + └NO3 + ┬ oxidation │ │ lipids (oils, soaps, skin oils) │ └ O3 + terpenes │ nicotine └ acid-base │ nicotine └ H+ + trimethylamine terpenes and other VOCs Condensed-phase chemistry ┬ oxidation │ └ O2 + lipids (oils) └ hydrolysis └H2O + resins, plasticizers, flame retardants chemistry takes place at surfaces Indoor Chemistry