Wavelength-Resolved Photon Fluxes of Indoor Light Sources: Implications for HO_x Production

Abstract

Photochemistry is a largely unconsidered potential source of reactive species such as hydroxyl and peroxy radicals (OH and HO, "HO") indoors. We present measured wavelength-resolved photon fluxes and distance dependences of indoor light sources including halogen, incandescent, and compact fluorescent lights (CFL) commonly used in residential buildings; fluorescent tubes common in industrial and commercial settings; and sunlight entering buildings through windows. We use these measurements to predict indoor HO production rates from the photolysis of nitrous acid (HONO), hydrogen peroxide (HO), ozone (O), formaldehyde (HCHO), and acetaldehyde (CHCHO). Our results suggest that while most lamps can photolyze these molecules, only sunlight and fluorescent tubes will be important to room-averaged indoor HO levels due to the strong distance dependence of the fluxes from compact bulbs. Under ambient conditions, we predict that sunlight and fluorescent lights will photolyze HONO to form OH at rates of 10-10 molecules cm s, and that fluorescent lights will photolyze HCHO to form HO at rates of ∼10 molecules cm s; rates could be 2 orders of magnitude higher under high precursor concentrations. Ozone and HO will not be important photochemical OH sources under most conditions, and CHCHO will generally increase HO production rates only slightly. We also calculated photolysis rate constants for nitrogen dioxide (NO) and nitrate radicals (NO) in the presence of the different light sources. Photolysis is not likely an important fate for NO indoors, but NO photolysis could be an important source of indoor O.

Formation and emission of hydrogen chloride in indoor air

“…After 30 minutes, HCl mixing ratios had decayed by 52%-62% of peak levels observed during the bleaching event. 42 Under these light conditions, photolysis reactions shown in Figure 3 could proceed. It is possible that photolysis could aid in the indirect formation of HCl.…”

“…It is possible that photolysis could aid in the indirect formation of HCl. 29,42 The Cl production rate at the light source represents the maximum production rate, while that at 1 m from the light source is the production expected at approximately human head height. All three are known to photolyze under ambient outdoor light to produce Cl atoms (eg, 22,24,27 ) which react with VOCs to form HCl ( Figure 3).…”

“…All three are known to photolyze under ambient outdoor light to produce Cl atoms (eg, 22,24,27 ) which react with VOCs to form HCl ( Figure 3). 42,49,50 Photochemical Cl production rates during the use of bleach may therefore exceed OH production rates under some conditions. 42 Under these light conditions, photolysis reactions shown in Figure 3 could proceed.…”

Predicting the importance of oxidative aging on indoor organic aerosol concentrations using the two‐dimensional volatility basis set (2D‐ VBS )

“…Higher HONO levels are caused by indoor combustion activities such as cooking with a gas stove . The indoor photolysis rate constant of HONO ( J ) under attenuated sunlight has been measured to be 1.26 × 10 −4 s −1 . Using indoor HONO measurements from Zhou et al .…”

“…34,52 The indoor photolysis rate constant of HONO (J) under attenuated sunlight has been measured to be 1.26 × 10 −4 s −1 . 53 Using indoor HONO measurements from Zhou et al 52 and the AER and assumed photolysis distributions described…”