## 3 Results and Discussion
### Fire Performance of Wood Parts Coated with PVAc-Bioadditive IFR Adhesive Blends
Table 9 summarizes the VOCs detected in the different stages of combustion (ignition, regime, and extinction). Thity-nine VOCs were identified, with aliphatic and aromatic hydrocarbons predominating, followed by amino acids and carboxylic acids. In addition, 12 compounds were found, possibly derived from the high-temperature reaction (combustion) between the functional groups of these families and other elements of the PVAc-bioadditive IFR adhesive blends. Figure 7: Uncoated and coated wood specimens with the IFR bioadditive after fire resistance test: (**a**) Uncoated wood; (**b**) Wood coated with PVAc; (**c**) Wood coated with PVAc-2.5% F1; (**d**) Wood coated with PVAc-12.5% F1; (**e**) Wood coated with PVAc-2.5% F2; (**f**) Wood coated with PVAc-5% F2; (**g**) Wood coated with PVAc-12.5% F2. In the combustion test, it was observed that the greatest quantity and variety of VOCs were emitted during the ignition (22 VOCs) and extinction (17 VOCs) stages when large volumes of carbon monoxide (CO) and VOCs are generated. This is a state that decreases with the ignition and permanence of the flame, which is why, during the regime or combustion in development, the occurrence of these decreased notably (8 VOCs) [88]. Thus, the beginning and end of combustion are the most critical stages from the environmental and public health point of view in fire-related incidents. Consequently, the highest amount of aliphatic and aromatic hydrocarbons was observed during the ignition stage in untreated wood, which presented emissions of ethylbenzene, p-Xylene, benzene, and toluene, which are all VOCs classified as carcinogenic [89; 90]. In the wood specimens coated with the PVAc- 12.5% F2 adhesive blend, the presence of ethylbenzene was also found in the ignition. At this stage, the first appearance of amino groups was observed from the wood specimens coated with the adhesive blends PVAc-12.5% F2 and PVAc-2.5% F2, probably caused by the decomposition of the protein-based IFR bioadditive at a high temperature. VOC ethanamine could have been originated from the transformation of the carboxylic group of valines into an alcohol by reacting with a reducing compound present in the system [91]. Cyclosiloxane, nitroalkane, anhydride-acid (pyruvate acid), and carboxylic acid ester compounds were also detected. Cyclosiloxane, formed by silicon and oxygen, could have been generated by the presence of silica in the PVAc adhesive to improve its physical mechanical performance since it was found in both the modified and unmodified samples [92]. The nitro groups come from the protein matrix of the IFR bioadditive, while the anhydro-acid is related to the decomposition of the bioadditive during combustion, possibly by yeast proliferation [93; 94]. The carboxylic acid ester, classified as a possible carcinogen [95], may be related to the composition of the commercial PVAc adhesive. In the combustion regime stage, the emission of aromatic hydrocarbons (such as benzene), typical of wood combustion [88; 96], as well as cyclic ethers (oxetane and epoxide), which can be formed when the temperature of the combustion process is reduced [97], was observed. In addition, the detected traces of alcohol-amine probably result from the reaction between alcohol compounds and amine groups on the IFR bioadditive protein during combustion [98]. This VOC was found in the specimens coated with PVAc 12.5% F2. In the extinction stage, the observed emissions corresponded to aliphatic and aromatic hydrocarbons (such as benzene), aromatic hydrocarbon-amine (benzene-amine), aldehyde group compounds, amino, furanoid, cyclosiloxane, ether-alkyl, carboxylic acid salt, and ester. The presence of furanoid VOC could be due to the hydrogenation of furtral, present in lignocellulosic biomass (wood), during the combustion process [99]. Ether-alkyl, the base component of PVAc adhesive [100], was identified as part of the polymeric base of the adhesive. The carboxylic acid salt (ammonium acetate) was formed by a reaction between ammonia and acetic acid [101].