Impacts of a clay plaster on indoor air quality assessed using chemical and sensory
measurements
Erin K. Darling
a
, Clement J. Cros
a
, Pawel Wargocki
b
, Jakub Kolarik
b
, Glenn C. Morrison
c
, Richard L. Corsi
a
,
*
a
Department of Civil, Architectural and Environmental Engineering, Cockrell School of Engineering, The University of Texas at Austin, 1 University Station C1786, Austin,
TX 78712, USA
b
International Centre for Indoor Environment and Energy, DTU Civil Engineering, Technical University of Denmark (DTU), Nils Koppels Allé, Building 402, DK-2800,
Kgs. Lyngby, Denmark
c
Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, 221 Butler-Carleton Hall, Rolla, MO 65409, USA
article info
Article history:
Received 22 February 2012
Received in revised form
3 May 2012
Accepted 9 June 2012
Keywords:
Perceived air quality
Clay
Ozone removal
Aldehyde
Passive removal
Green material
abstract
Passive removal materials (PRMs) are building materials or furnishings that effectively control indoor
pollution without substantial formation of chemical byproducts and without an energy penalty. Recent
studies have suggested that clay might be an effective PRM for ozone. To assess clay wall plaster as a PRM
for improving air quality by controlling ozone, perceived air quality (PAQ) was determined in the
presence of eight combinations of an emitting and reactive pollutant source (new carpet), clay plaster
applied to gypsum wallboard, and chamber air with and without ozone. A panel of 24 human subjects
assessed air quality in twin 30 m
3
chambers using a continuous acceptability scale. Air samples were
collected immediately prior to panel assessment to quantify concentrations of C
5
eC
10
saturated n-
aldehydes and two aromatic aldehydes that are commonly produced by reaction of ozone with carpet.
Perceived air quality was most acceptable and concentrations of aldehydes were lowest when only clay
plaster or both clay plaster and carpet were present in the chambers without ozone. The least acceptable
PAQ and the highest concentrations of aldehydes were observed when carpet and ozone were present
together; addition of clay plaster for this condition improved PAQ and considerably decreased aldehyde
concentrations.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Increasing levels of tropospheric ozone have been related to
numerous adverse effects on humans, including decreases in short-
term lung function [1,2], increased rates of asthma symptoms in
infants [3], and increases in morbidity and both non-traumatic
mortality and cardiopulmonary death rates [4e6]. While much of
the attention paid to ozone tracking, modeling, and reduction has
focused on outdoor ozone, approximately 40e60% of population
exposure to ozone of outdoor origin occurs indoors [7]. In addition,
many sources of ozone exist indoors, including laser printers,
photocopiers, and ion generators [8e11]. The indoor contribution
to ozone exposure is probably greater for vulnerable populations,
e.g., infants, elderly, and chronically ill, due to the greater average
amount of time they spend indoors [7,12,13].
Ozone reacts with numerous chemicals in indoor environments.
These reactions lead to the formation of oxidized reaction products,
which can be toxic, irritating to mucosal membranes and other
tissues, and harmful to indoor materials [14]. At low building air
exchange rates the time for these reactions to occur and the resi-
dence times of reaction products increase [15]. Consequently,
cumulative molar intake of ozone byproducts can be as high as
twice the intake of unreacted ozone [7], and therefore decreases in
indoor ozone concentrations are an important part of reducing total
population exposure to both ozone and ozone reaction products.
Interestingly, there have only been a few studies on sensory eval-
uations related to the effects of ozone reactions with interior
building materials [16]; in particular, carpet exposed to ozone
produced the most negative effect on sensory perceptions
compared to other building materials, including carpet not exposed
to ozone.
Indoor ozone concentrations can be lowered by treating
building intake air with activated carbon [17,18], using fibrous
activated carbon filters in Heating, Ventilation, and Air Condi-
tioning (HVAC) systems, or alternatively by strategically placing
ozone-scavenging materials indoors [19]. The latter approach, i.e.,
application of passive removal materials (PRMs), should involve
coverage of large surface areas, appear aesthetically acceptable, and
*
Corresponding author. Tel.: þ1 512 471 3611; fax: þ1 512 471 5870.
E-mail address: corsi@mail.utexas.edu (R.L. Corsi).
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Building and Environment
journal homepage: www.elsevier.com/locate/buildenv
0360-1323/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.buildenv.2012.06.004
Building and Environment 57 (2012) 370e376