*Article* **Investigating the Emission of Hazardous Chemical Substances from Mashrabiya Used for Indoor Air Quality in Hot Desert Climate**

**Chuloh Jung \* and Nahla Al Qassimi**

Department of Architecture, College of Architecture, Art and Design, Healthy and Sustainable Buildings Research Center, Ajman University, Ajman P.O. Box 346, United Arab Emirates; n.alqassimi@ajman.ac.ae **\*** Correspondence: c.jung@ajman.ac.ae

**Abstract:** Dubai has the reputation of a continuously growing city, with skyscrapers and mega residential projects. Many new residential projects with poor choices of material and ventilation have led to a faster rise in sick building syndrome (SBS) in Dubai than in any other country, and the IAQ (indoor air quality) has become more critical. Volatile organic compounds (VOCs) and formaldehyde (HCHO) affect the health of residents, producing the phenomenon known as SBS (sick building syndrome). It has been reported that wood materials used for furniture and wooden windows and doors are a significant source of indoor air pollution in new houses. This paper aims to identify the factor elements emitting harmful chemical substances, such as VOCs and HCHO, from wooden mashrabiya (traditional Arabic window) by examining the characteristics of the raw and surface materials through test pieces. As a methodology, a small chamber system was used to test the amount of hazardous chemicals generated for each test piece. For Total volatile organic compounds (TVOC) and HCHO, the blank concentration before the injection and the generation after seven days were measured. The results showed that to reduce TVOC, it is necessary to secure six months or more as a retention period for raw materials and surface materials. The longer the retention period, the smaller the TVOC emission amount. In the case of mashrabiya, an HCHO low-emitting adhesive and maintenance for one month or more are essential influencing factors. It was proven that using raw materials with a three-month or more retention period and surface materials with a one-month or more retention period is safe for indoor mashrabiya. This study is the first study in the Middle East to identify factors and characteristics that affect the emission of hazardous chemicals from wood composite materials, such as wood mashrabiya, that affect indoor air quality in residential projects in Dubai. It analyzes the correlation between emission levels and the retention period of raw and surface materials, in order to provide a new standard for indoor air pollutants.

**Keywords:** mashrabiya; total volatile organic compounds (TVOC); formaldehyde (HCHO); retention period; hot desert climate

### **1. Introduction**

From the point of view of selecting building materials in the design stage of a house, it is helpful to use data on the amount of hazardous chemical substances generated from each building material [1,2]. In the case of using construction materials with a large amount of hazardous chemical substances, more ventilation is required to meet a certain concentration standard than when using low-generation building materials. In a hot desert climate, this leads to an increased energy consumption [3]. Therefore, it is desirable not only in terms of comfort and health, but also in an energy-saving aspect to use materials that generate low-toxicity substances [4].

In the United Arab Emirates (UAE), the Emirates Green Building Council launched the Energy Efficiency Program (EEP) in 2013 to reduce the carbon footprint for existing energyinefficient buildings [5]. The EEP database was launched in 2014 to facilitate building retrofit

**Citation:** Jung, C.; Al Qassimi, N. Investigating the Emission of Hazardous Chemical Substances from Mashrabiya Used for Indoor Air Quality in Hot Desert Climate. *Sustainability* **2022**, *14*, 2842. https:// doi.org/10.3390/su14052842

Academic Editor: Diego Pablo Ruiz Padillo

Received: 3 January 2022 Accepted: 14 February 2022 Published: 28 February 2022

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projects, and the Technical Guidelines for Retrofitting Existing Buildings was published in 2015 [6]. After the guidelines, Building Retrofit Training (BRT) was launched in 2017 by the Dubai Supreme Council of Energy and Masdar to increase the fundamental knowledge of retrofits specific to the MENA (Middle East/North Africa) region [6].

During this process, the recent construction of energy-efficient houses in Dubai has become more air-tight [7]. Accordingly, the importance of air quality in the indoor environment of a house is increasing [8]. In particular, it is known that indoor air pollution caused by chemicals such as volatile organic compounds (VOCs) and HCHO affects the health of residents [9].

According to the Dubai Healthcare City report, an estimated 15% of Dubai residents have suffered sick building syndrome (SBS) symptoms, such as fatigue, headache, red eyes, eye/nose/throat irritation, dry cough, dry or itchy skin, dizziness, and difficulty in focusing on work [10,11]. Due to this SBS phenomenon, the Dubai Municipality initiated the indoor air quality (IAQ) concentration standards, requiring less than 0.08 ppm (parts per million) of HCHO, less than 300 micrograms/m<sup>3</sup> of total volatile organic compounds (TVOCs), and less than 150 micrograms/m<sup>3</sup> of particulate matter (PM10) (less than 10 microns) in 8 h of continuous monitoring prior to occupancy for new houses [12].

In previous studies, it has been reported that wood materials used for furniture and wooden windows and doors are a significant source of indoor air pollution in new houses [13]. It should be noted that wood products emit hazardous chemical substances continuously for an extended time, since the emission characteristics of hazardous chemicals from wood over time are different from those of hazardous chemical substances generated from paints and adhesives [14,15].

In particular, in the case of new houses, the amount of built-in furniture is increasing [16]. As the risk of indoor contamination by hazardous chemical substances generated in wood materials during construction increases, the need for the control of this has also increased [17]. These wood products are applied indoors as a composite material, rather than a single wood product, formed by applying different surface materials, such as a particle board (PB) or medium-density fiberboard (MDF), and going through various processing methods [18]. In addition, the installation of these wood products follows a process in which partially finished products are brought into the room, with a time gap according to the process, and are installed and finished onsite [19]. Therefore, it is possible to reduce, to some extent, the natural emission of toxic chemical substances from wood materials by making adjustments to such factors as the retention period on site during the installation process [20].

Indoor wood products are molded from composite materials rather than single materials, and identifying the emission characteristics of hazardous chemical substances could be helpful in improving indoor air quality [21,22].

Currently, wood materials mainly used for new houses in Dubai can be classified into mashrabiya (Figure 1) and built-in furniture materials.

The influencing factors can be derived by reviewing the previous literature on the emission characteristics of hazardous chemical substances from single materials or composite materials from furniture and wooden windows/doors.

Several researchers have conducted research on the emission characteristics of chemical substances emitted from wood materials, such as furniture and wooden windows/doors [23]. Adamová et al. (2020) [24] and Ulker et al. (2021) [25] report that, unlike the emission process of paints or adhesives, chemicals in wood materials are continuously emitted into the air in trace amounts for a very long time. Their research focuses on single materials such as plywood, PB, and MDF.

Richter et al. (2021) [26] reports the effect of a single material combination on the emission of pollutants from composite finishing materials, since the building finishing materials mainly used in houses are composite finishing materials. For the composition of the test piece, a composite material composed of wallpaper and adhesive or floorboard and adhesive was used in the experiment. The release mechanism was estimated based on the results showing the difference in the emission amount of the composite material according to the difference in the contaminant content of the single material constituting the composite material. The amount of composite materials emitted differs depending on the composition of the single material and the degree of contamination.

**Figure 1.** Wooden mashrabiya window at Dubai Hill Estate.

Cao et al. (2019) [27] reports that MDF is treated with low-pressure melamineimpregnated paper (LPM), which is a surface method for furniture materials, on both sides, and those that were not treated were targeted. The experiment was carried out with differences in the exposure of the cut surface in the case of the MDF-treated material on both sides. As a result, the emission intensity tended to increase as the ratio of the cut surface increased (the surface finish area decreased). It was reported that most of the wood materials showed a difference in the amount of emission depending on the surface finishing method.

Qi et al. (2019) [28] produced six types of built-in furniture by selecting furniture composed of raw materials and surface finishing materials commonly used in apartments and identified the chemical pollutant emission characteristics by raw material grade and surface finish. This study reported that the concentration of HCHO was different depending on the core material in the same surface finishing material.

Xiong et al. (2019) [29] reports that the emission of TVOC is not affected by the grade of the core material, but is affected by the finish of the surface material. In the TVOC case, the raw material grade influences and the difference in the quantity of emission by the surface material were established.

Through the above literature review, in the case of a wood composite finishing material, very diverse factors affect the emission of hazardous chemical substances. The degree of contamination of single raw materials or surface materials, differences in surface finishing methods, and the retention period of raw materials constituting composite finishing materials were identified as factors affecting the release of hazardous chemical substances [30].

The purpose of this study is to identify the factors emitting harmful chemical substances from wooden mashrabiya by examining the characteristics of the raw materials and surface finishing materials of the test pieces.

#### **2. Materials and Methods**

*2.1. Types and Characteristics of Raw Materials*

2.1.1. Fiberboard

Fiberboard is a generic term for plate products formed by fiberizing wood or other plants and is classified according to density [31]. Since fiberboard has a dense structure and excellent machinability, it can be used instead of general wood for construction sites that require precise dimensions or for frames and moldings that require accurate angles [32]. The Environmental Protection Agency (EPA) in the United States has classified the above materials according to the amount of HCHO emission since 2018 [33] (Table 1).



It is classified as MDF with a density of less than 0.35 g/cm3–0.85 g/cm<sup>3</sup> , and HB with a density of 0.85 g/cm<sup>3</sup> or more. MDF is the most used and can be produced from 3.0 mm to 30 mm thick [34] (Figure 2).

**Figure 2.** HB (**left**), MDF (**middle**), and glued laminated timber (**right**).

2.1.2. Glued Laminated Timber

Glued laminated timber refers to a material that is laminated and adhered in the length, width, and thickness directions by paralleling each other in the fiber direction using sawmills, boards, or small square materials [35] (Figure 2). Additionally, it refers to a material that is decorated on the surface of the aggregated material for aesthetics.

Dissimilar to plywood by orthogonal and odd-sheet lamination methods, glued laminated timber is not manufactured in a plate shape, and it is manufactured in various shapes and sizes depending on the purpose of use. It is mainly used as a wooden frame material for windows and doors and as a core material for doors, and one of the most popular glued laminated timbers is Lauan laminated timber (LLT).

### *2.2. Types and Characteristics of Surface Finishes*

#### 2.2.1. Veneer

Veneer refers to a product manufactured by processing raw wood as thin as paper [36]. It is used as a decorative material to express the naturalness and splendor of wood. It is a material that can express the texture of wood by finishing the primary structural frame with

gypsum board or plywood, applying adhesive to the surface, and attaching it by heating and pressing methods [37]. In most cases, it is usually composed of a thin plate of 0.2 mm, and it is rarely used as an exterior material.

For the sample used in this experiment, samples prepared by wrapping veneer around raw materials of LLT, MDF, and HB, used for mashrabiya, were used with hot-melt-type adhesive [38].

#### 2.2.2. Polyvinylchloride (PVC) Sheet

PVC sheet is manufactured by mixing polyvinyl chloride as a raw material with stabilizer, plasticizer, and pigment [39]. Since it is easy to process and mass production is possible, it is currently widely used as a surface material for overlay or wrapping of interior materials, furniture, and wooden windows and doors.

For the sample used in this experiment, a sample piece wrapped around PB was used with a water-based liquid adhesive.

#### 2.2.3. Finishing Foil (F/F)

It is a patterned paper in which paper is impregnated with thermosetting resin (melamine, urea, and acrylic), and then the surface is painted [40]. This material was developed to reduce the cost of LPM. Dissimilar to LPM, an additional adhesive must be used to bond the finishing foil. In the Middle East, it is commonly used as an interior building material and furniture surface finishing material [41].

For the sample used in this experiment, the sample was wrapped in raw materials of LLT, MDF, and HB, and the finishing foil with a hot-melt adhesive precoated on the backside was used.
