The finest particles in dust after sanding untreated and thermally modified spruce, oak and meranti wood

doi:10.21203/rs.3.rs-2214433/v1

Download PDF

Research Article

The finest particles in dust after sanding untreated and thermally modified spruce, oak and meranti wood

https://doi.org/10.21203/rs.3.rs-2214433/v1

This work is licensed under a CC BY 4.0 License

Journal Publication

published 30 Jul, 2023

Read the published version in European Journal of Wood and Wood Products →

Version 1

posted

You are reading this latest preprint version

Airborne wood dust causes health and safety hazards in the construction and furniture industry. The research verified whether the thermal modification affects the share of the finest dust particles, smaller than < 10 µm, in the wood dust. The experimental research included nine variants of materials (untreated and thermally modified – in 160°C by 3 h and in 220°C by 3 h – oak, spruce, and meranti wood). The dust was generated with a belt sander (P120 sandpaper, 14.5 m/s belt speed, and 0.65 N/cm² pressure). The four fractions with particle sizes < 25, 25–80, 80–250, and > 250 µm, were assessed with sieves with aperture sizes of 25, 80, and 250 µm. The content and size distribution of the finest particles in the fractions were measured with laser particle sizer. The results suggest that: (1) both untreated and thermally modified oak wood dust show the higher share of the finest particles in comparison to spruce and meranti wood. (2) Dust from thermally modified oak and meranti has a lower content of harmful particle fractions than dust from untreated wood. The opposite was observed in the case with spruce wood because spruce dust has a low content of fine fractions and its particles have a more irregular elongated shape. (3) The study took into account the extreme temperatures used in the thermal modification of wood (160 and 220°C), then it can be assumed that the two statements mentioned above are valid in all intermediate temperatures.

Meranti

Oak

Spruce

Sessile oak

Norway spruce Thermal treatment

Sanding

Dust

Wood dust

Sieve analysis

Laser diffraction methods

Particle-size distribution

Woodworking generate wood particles of various sizes and shapes. In industrial production systems, these particles are collected by local exhaust ventilation and transported through piping systems from the generation space to waste disposal units that collect this organic material as energetic and construction by-products. Unfortunately, the finest wood particles tend to become an inhalable particulate matter and can harm human health by breathing in, skin contact, or eye contact. A legal limit in the United States for an employee's exposure to wood dust in the workplace is 15 mg/m³ total exposure and 5 mg/m³ exposure over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended maximum exposure level of 1 mg/m³ of inhalable exposure to total dust. The long exposure of around 1 mg/m³ to airborne wood dust is a mucous membrane irritant and may cause dermatitis, allergic respiratory effects, mucosal and nonallergic respiratory effects, as well as cancer (Wood Dust and Formaldehyde, (1995)). The American Conference of Governmental Industrial Hygienists (ACGIH) recommends a 0.5 mg/m³ limit for wood species not suspected as human carcinogens. The ACGIH lists oak and beech as confirmed carcinogenic species and highlights birch, mahogany, teak, and walnut as suspected carcinogenic species. The value is below the 2 mg/m3 permissible limit (BOELV) for the inhalable fraction of hardwood dust, introduced by the European Commission (2017/2398/UE), which will be valid in the EU countries as of 18 January 2023 (a 3 mg/m3 is a permissible limit during the actual transition period). If hardwood dust is mixed with other dust types, the concentration limit value applies to all wood dust in this mixture.

Airborne wood dust usually consists of particles up to 100 µm. The fractional composition and the amount of dust suspended in the air are not constant. The larger the particle, the heavier and faster it sinks to the ground. An inhalable fraction of the airborne wood dust consists of particles that enter the human respiratory tract during breathing. Inhaled airborne dust particles, not stopped into the nose, penetrate through the pharynx and the larynx, are a thoracic fraction (≥ 10 µm, according to WHO definition). Respirable fraction (≥ 4 µm) can penetrate the lower respiratory tract (trachea, bronchus, and lungs). The wood dust emitted into the air during woodworking contains respirable particles consisting of inhalable, thoracic, and respirable fractions. The mass share of the respirable fraction of airborne sawdust is usually up to 30%. The sizes of wood particles depend on the type of woodworking, the technology parameters used, and the type of wood.

Wood dust also causes other hazards. Airborne sawdust is highly explosive. The dust of the finest particles dispersed in the air at a sufficient concentration in a confined area may explode when affected by an ignition source (Callé et al. 2005). Wood dust adversely affects the complex mechanisms of modern industrial devices, pollutes the lubricant, hinders movement, and disables optical surveillance over industrial processes.

The literature data confirm that sanding technology influences the size of the dust particles. For example, in sanding, the mean particle size of the dust obtained with P60 sanding paper was 1.4 times larger than that of the dust obtained with P180 granulation sanding paper (Pędzik et al. 2020). The blunt level of sanding paper is another factor affecting the particle size distribution (Sydor et al. 2021). The type of wood (hardwood or softwood) also significantly influences the particle size and the content of the dust fraction with the finest particle sizes. The content of the finest particles in dust ranged from 0.21% for pine (P60 sanding paper) to 12.58% for beech (P180 sanding paper) (Pędzik et al. 2020).

The heat treatment also influences the particle size distribution. Heat is used in many wood technologies, for example, in the steam kiln drying of lumber, in steam wood aging, in hot-air drying of veneer, in hot-press gluing, in wood densification, in steam solid wood bending, and in solid wood properties modification. An industrial-scale wood modification process by temperature was developed in 1993 in Finland (Pertti et al. 1997). Wood heated for several hours at high temperatures (up to 250°C) with aqueous vapor to change its physical properties. These changes resulted in a reduced volumetric mass density, improved dimensional stability, and increased resistance against biological factors (Stamm and Hansen 1937). Some strength properties are deteriorated, making the wood more fragile (van Blokland et al. 2020). Particles resulting from the woodworking of thermally modified wood are generally finer (Majka et al., 2022). The smaller particle size of the wood dust from the wood after thermo-modification makes it more likely to be respirable.

These reasons: protection of employees' health, the willingness to collect the entire valuable wood by-product, safety against fire, reliability of industrial equipment and changed wood properties by heat treatment, justify research and analysis of the airborne finest wood dust fractions. This research aimed to characterize the finest dust particles that can form a thoracic fraction when dispersed in the air, with sizes < 10 µm, generated by sanding of untreated and thermally modified meranti, oak, and spruce wood. We hypothetize that the temperature of thermal modification affects the share of the finest, harmful dust particles generated during the sanding of thermally modified wood.

Experimental samples

Norway spruce (Picea abies) and Sessile oak (Quercus petraea) were collected in Vlčí jarok (Budča, Slovakia), at 440 m above sea level. Meranti (Shorea acuminata) was purchased from the sub-provider (Wood Store, Prague, Czech Republic). Radial boards were cut from the logs and processed in test samples measuring 20 × 100 mm with a length of approximately 700 mm. The samples were then dried to a residual moisture of 8%. The entire process was performed in the Research and Development Workshops of the Technical University in Zvolen (Zvolen, Slovakia). Five samples were prepared for each treatment. measuring 20 × 100 × 700 mm.

Heat treatment and sample processing methods

The processed samples were thermally modified in the Arboretum FLD (Czech University of Life Sciences, Prague, Czech Republic) in the town Kostelec nad Černými lesy. The S400/03 (LAC Ltd., Rajhrad, Czech Republic) chamber, shown in Fig. 1, was used for thermal modification, designed to heat the wood with ThermoWood technology.

The main parameters of the chamber are presented in Table 1.

Table 1

Chamber parameters S400/3.
Parameter	Value
Maximal temperature (°C)	300
Volume (l)	380
External dimensions, W×D×h (mm)	1400×1850×1200
Internal dimensions, W×D×h (mm)	800×800×600
Weight (kg)	350
No of fans	1
Input (kW)	6.0

The thermal modification was conducted at 160 and 220°C; the used procedure was as follows:

application of temperature and a humidity sensor, putting the samples in the chamber, closure and locking of the chamber door,
setting of the thermal modification temperatures and times (steepness in°C/h for heating and cooling phases),
thermal modification of samples in six phases: first phase – increase of temperature to 40°C, second phase – increase of temperature to 130°C, drying, third phase – heat treatment – heating to working temperature, fourth phase – heat treatment – working temperature of 3 hours, fifth phase – cooling to 130°C and humidity treatment, sixth phase – cooling to 60°C with humidity treatment at the level of 4-7%. The process is complete when the temperature reaches 60°C.
sample extraction from the chamber.

The used thermal modification methodology of samples is published in the previously papers of (Kučerka and Očkajová 2018) and (Očkajová et al. 2018a).

Dust generation by sanding

In laboratory experiments a narrow belt sander (JET JSG-96 (JPW Tool AG, Fällanden, Switzerland), with a belt speed of 10 m·s^-1, and a sanding belt (HIOLIT XO P 80, KWH Group Ltd., Vaasa, Finland) were used. For each of the nine sample variants a fully new sharp sanding belt was used. Figure 2 presents the laboratory sander used.

Wood dust was captured using a Rowenta vacuum cleaner (Banská Bystrica, Slovakia) into Rowenta Original ZR 814 to disposable paper bags. A new paper bag was used for each of the nine sample variants. At the end of each sanding, the sample from the paper bag was poured into a plastic bag, which was closed with a flexible wire to avoid changing the parameters. Approximately 200 g of each sample was collected, and 30 grams was the weight for each test.

Sieve Particle-size analysis

The wood dust particle-size distribution was tested by sieving. A standard kit of several sieves ordered vertically (2000, 1000, 500, 250, 125 µm, and the bottom collector – dust particles passed through all of the mesh screens) was placed on the vibrating stand of the sieving machine (Retsch AS 200c; Retsch GmbH, Haan, Germany) with an adjustable sieving interruption frequency (20 s) and a sieve deflection amplitude (2 mm/g), following STN 153105/STN ISO 3310-1 (2000) standard. As much as 30 g of material was analyzed in each treatment. Each treatment was exposed to six sieving processes.

The particle-size distribution was obtained by weighing the remaining wood dust on the sieves after sieving on the Radwag WPS 510/C/2 electronic weighing scale (Radwag Balances and Scales, Radom, Poland), with a capacity of 510 g and an accuracy of a scale with the resolution of 0.001 g. The weight figures for each sieve were recorded in MS Excel (Microsoft Corporation, Redmond, WA, USA), and the results were statistically evaluated using STATISTICA 13 software (TIBCO Software Inc., Palo Alto, CA, USA).

Laser particle sizer analysis

Sieve analysis provides only a general particle-size distribution without any information on the mass concentration of very fine dust fractions. The Analysette 22 Microtec Plus (Fritsch, Idar-Oberstein, Germany) laser particle sizer was used to specify details regarding the size of the dust particles smaller than 125 µm (collected in the bottom collector) which can be inhalable when dispersed in the air. The laser particle sizer automatically measures a particle size according to a predetermined Standard Operating Procedure and theoretical assumptions. The obtained results were processed by MaScontrol software (Fritsch, Idar-Oberstein, Germany). It gives two types of quantities: the sum of the distribution Q(x) and the density of the distribution q(x).

According to dQr(x) = qr(X) dx, qr(x) is a component of dQr(X), which is contained in the interval dx for particles from x and x + dx. The result is a random variable r (when r = 3, means volume distribution), where:

$${q}_{r}\left(x\right)=\frac{{x}^{r}\bullet {q}_{0}\left(x\right)}{\sum _{i=1}^{n}{x}_{i}^{r}\bullet {q}_{0i}\left({x}_{i}\right)}=\frac{{dQ}_{r}\left(x\right)}{dx}$$

Based on this distribution, the contents of the particles in the assumed size ranges (C_Li) of dust collected in the bottom collector (C_S125) were determined by MaScontrol software. The most critical particle size ranges from the point of view of human respiratory tract penetration (< 2.5 µm, 2.5–4 µm, 4–10 µm) were used to calculate the content of fine particles in the total mass of dust.

Calculation of the finest particles content

The calculation of the content of particles < 2.5 µm, 2.5–4 µm, 4–10 µm in the whole mass of dust created was performed as follows:

c _i=c_S125⋅c_Li

where c_i—dust content in the assumed size range of the whole mass of dust, c_S125—dust fraction collected during the sieve analysis in the bottom collector, and c_Li—mass fractions of the dust in the assumed ranges determined using laser diffraction analysis in the C_S125 fraction.

This calculation method has been already used for the determination of the finest dust fractions in many earlier studies (Rogoziński et al. 2021; Pędzik et al. 2021).

The results of the sieve analysis are shown in Table 2. The sanding dusts generated in this study are fine. The fraction of the dust with the greatest mass share is always the fraction collected in the bottom of the set of sieves below the sieve 0.125 mm. There are some differences in the value of this share. For each wood species, the lowest percentage was measured in the case of dust created during the sanding of the wood modified at 220°C. It suggests that the modification temperature can influence the sanding process. At the highest temperature, coarser dust is generated during sanding. But the sieve analysis can provide only a general particle-size distribution the particle content have to be determined using a complementary method.

Table 2

Particle-size distribution of dust variants by sieving method.
Sieve aperture size (µm)	Percentage share of dust fractions
	Spruce			Oak			Meranti
	untreated	modified at 160°C	modified at 220°C	untreated	modified at 160°C	modified at 220°C	untreated	modified at 160°C	modified at 220°C
Bottom	86.11	92.63	61.68	94.72	92.1	73.68	84.17	87.18	74.48
125	13.25	7.14	34.3	4.48	4.18	18.28	14.95	11.18	24.12
250	0.35	0.1	3.87	0.6	1.18	6.42	0.71	0.45	1.41
500	0.15	0.1	0.15	0.2	2.44	1.52	0.2	0.1	0
1000	0.15	0.05	0	0	0.1	0.1	0	0.1	0
2000	0	0	0	0	0	0	0	0	0

The results of the particle-size distribution by laser diffraction method are shown in Fig. 3. The distributions depicted on the graphs were used for the determination of the particles contents in the assumed size ranges (C_Li) of dust collected in the bottom collector (C_S125).

Based on the above results, the content of particles < 2.5 µm, 2.5–4 µm, 4–10 µm in the whole mass of dust created was calculated. The results of statistical analysis and direct comparison of these contents are shown in Table 3 and Fig. 4.

Table 3

Analysis of variance (ANOVA) tables for the finest particle content of untreated and thermally modified spruce, oak, and meranti wood dust, taking into account the effect of heat treatment and particle size
	Effect	SS	df	MS	F-value	p-value
Spruce	Intercept	80.20411	1	80.20411	92.74634	0.000000
	Heat treatment (factor a)	16.12952	2	8.06476	9.32592	0.000260
	Particle size (factor b)	20.80817	2	10.40408	12.03106	0.000033
	a × b	6.66957	4	1.66739	1.92814	0.115497
	Error	59.66902	69	0.86477
Oak	Intercept	1208.43	1	1208.43	668.787	0.000000
	Heat treatment (factor a)	236.822	2	118.411	65.5327	0.000000
	Particle size (factor b)	627.237	2	313.618	173.5674	0.000000
	a × b	128.393	4	32.098	17.7642	0.000000
	Error	124.676	69	1.807
Meranti	Intercept	478.7123	1	478.7123	642.0294	0.000000
	Heat treatment (factor a)	137.7533	2	68.8766	92.3745	0.000000
	Particle size (factor b)	287.0063	2	143.5032	192.4606	0.000000
	a × b	68.85080	4	17.2127	23.085	0.000000
	Error	49.2112	66	0.7456
SS – the sum of squares, df – degrees of freedom, MS – mean squares, F – Fisher's F-test

The analysis of variance confirms the significant importance of the influence of the prior thermal modification (factor a) on the dimensional characteristics of the dust generated during wood sanding and the share of the finest particles fractions of the dust (factor b), which, when dispersed in the air, may constitute thoracic and respirable dust. Furthermore, the interaction between factors (a) and (b) was confirmed in the case of oak and meranti wood dust. In the case of spruce wood dust, there is no such interaction (marked gray row in Table 3).

Among the examined cases, oak wood dust is characterized by the highest average proportion of the finest particles (of all assumed ranges, i.e., < 2.5, 4, and 10 µm). This statement applies to both untreated and thermally modified wood dust. Overall, these results suggest that sanding dust from thermally modified wood is characterized by a lower average fraction of potentially harmful particles which, when dispersed in the air, may constitute thoracic and respirable dust (for all levels of discrimination – size ranges) than for sanding dust from untreated wood. This regularity is not confirmed only by the results of the analysis of dust samples from spruce wood.

Table 3

Statistical analysis of fine particle content (%) of untreated and thermally modified spruce, oak and meranti wood dust
		Particle content (%)
	Treatment option	< 2.5 µm	< 4 µm	< 10 µm
Spruce	Untreated	0.49 ^ab ±0.39	0.62 ^ab ±0.49	1.40 ^ab ±1.55
	Thermally modified at 160°C	0.86 ^b ±0.48	1.13 ^b ±0.64	2.93 ^b ±1.99
	Thermally modified at 220°C	0.36 ^a ±0.22	0.46 ^a ±0.35	0.90 ^a ±0.76
Oak	Untreated	2.72 ^b ±0.39	3.67 ^b ±0.43	12.90 ^b ±1.64
	Thermally modified at 160°C	1.28 ^a ±0.41	1.43 ^a ±0.58	4.47 ^a ±2.14
	Thermally modified at 220°C	0.98 ^a ±0.42	1.63 ^a ±0.65	6.46 ^a ±2.69
Meranti	Untreated	2.00 ^b ±0.40	2.24 ^b ±0.43	9.01 ^b ±1.94
	Thermally modified at 160°C	0.82 ^a ±0.09	0.85 ^a ±0.24	3.21 ^a ±0.72
	Thermally modified at 220°C	0.49 ^a ±0.06	0.58 ^a ±0.12	3.62 ^a ±1.29

Mean value (n = 9) ± standard deviation; identical superscripts (a, b, c) indicate non-significant difference (p < 0.05) between mean values according to post hoc Tukey's test.

The results of the statistical analysis show that the average content of the finest dust fractions isolated from the dust generated during the sanding of oak and meranti wood does not depend on the parameters of the previous thermal modification process. In the discussed cases, the average contents of these dust fractions (for all levels of discrimination – size ranges) generated during the sanding of modified wood at 160 and 220 ° C do not differ significantly (for p < 0.05).

(Kučerka and Očkajová 2018) studied the dust of Sessile oak (Quercus petraea) and Norway spruce (Picea abies). The wood, after the thermal modification in four variants of temperatures, 160, 180, 200, and 220°C, by 3h, was sanded on a vertical narrow-belt sander with P80 paper. The set of sieves with aperture sizes 2000, 1000, 500, 250, 125, 80, 63, 32 µm was used in the sieve analysis. The finest particle size fraction (≤ 80 µm) of oak dust showed the highest proportion for all treatment temperatures; simultaneously, the lowest values of dust fraction with a value of ≤ 80 µm were obtained at the processing temperature of 220°C in case of both studied wood species. The authors pointed out that the increase in treatment temperature does not significantly affect the amount of dust generated. The authors explained the high amount of the finest particle created during sanding by the decreased wood density resulting from increased temperature during the modification process.

(Očkajová et al. 2019) studied the relationship between the density of untreated wood, wood after thermal modifications at four temperatures (160, 180, 200, and 220°C), and the properties of dust created by sanding with a belt sander using P80 sanding paper. Three species of wood were tested: Sessile oak (Quercus petraea), Norway spruce (Picea abies), and Meranti (Shorea acuminata). A set of sieves, 2000, 1000, 500, 250, 125, 80, 63, 32 µm, was used to assess the dust size distribution. The proportion of fine particles (≤ 80 µm) in thermally modified oak dust was similar to that of untreated wood's fine dust. This share was 92–95%. A significant decrease in the mass share of this fraction was observed in the dust from wood modified at 220° C. The highest share of dust with a particle size of ≤ 80 µm for other wood species was measured in dust from modified wood at a temperature of 160° C (87% - meranti, 93% - spruce). This share decreased with the increasing temperature of wood modification. A similar influence of temperature was observed in the smallest sieve fraction (32 µm) and on the bottom of the sieve (a fraction with the smallest particle sizes). The authors explained the sieve analysis results with the reduced density of thermally modified wood.

The processing technology influences the particle size distribution in wood dust. (Očkajová et al. 2020b) studied the granulometric composition of chips and dust from the longitudinal milling and sanding of thermally modified oak and spruce wood at four modification temperatures: 160, 180, 200 and 220°C. Sieve analysis inluded 2000, 1000, 500, 250, 125, 80, 63, and 32 µm sieves. The results showed that the residual curves show the difference in particle size distribution in the two technologies. The sanding dust residue curves shift to the right due to the increased temperature of the wood treatment (higher proportion of large particles), while the milling dust residue curves shift to the left due to the increased temperature of the wood treatment (higher proportion of small particles). This observation is also confirmed by earlier literature reports on oak sanding dust (Marková et al. 2016; Očkajová et al. 2018b).

(Očkajová et al. 2020a) studied the particle size distribution in dust generated during longitudinal milling of thermally modified spruce and oak. The variables in experiment were the modification temperature (160, 180, 200, and 220°C), and the feed rate (6, 10, and 15 m·min^− 1). The particle size distribution measurements was made with a set of sieves (2000, 1000, 500, 250, 125, 80, 63, and 32 µm). The authors obserwed that the mass share of the coarse, fine, and very fine dust fractions changes with the increasing wood modification temperature. The study results demonstrated that the amount of sieve fraction with particles ≤ 80 µm, increased in oak and spruce, only after applying the highest temperatures, i.e. 200 and 220°C.

(Kminiak and Dzurenda 2019) investigated the changes in the particle size distribution of wood chips due to thermal wood treatment. They used maple (Acer pseudoplatanus) wood particles formed during milling in a 5-axis CNC machining center for analysis. The analysis showed that more than 2/3 of the dust particles produced were coarse-grained fractions > 100 µm. The share of particles with a size smaller than 125 µm, did not exceed 2.5%. The thermally modified maple wood did not form the dangerous finest dust particles. The results did not confirm the thesis suggested by earlier authors that changes causing an increased share of fine dust fraction occur as a result of the heat treatment on the wood's chemical structure.

The cited research results suggest that the thermal modification reduces the dust fraction with a particle size ≤ 80 µm. An example is the cited study of dust waste from sawing oak and pinewood (Dzurenda et al. 2010), milling and sanding oak and spruce wood (Očkajová et al. 2020b, a). On the other hand, in scientific publications on the dust generated during sanding thermally modified wood (oak, spruce, meranti), based on the sieve analysis performed, a lower content of particles with the smallest size was found in the dust from the wood modified at the highest temperature (220°C) ) (Kučerka and Očkajová 2018; Očkajová et al. 2019). The absence of the finest particles, i.e. < 32 µm, was also found. (Kminiak and Dzurenda 2019) proposed a similar conclusion based on their research on dust from milling maple wood. The authors also stated that there were no significant differences in particle sizes for modified and untreated wood dust.

Such statements contradict the research results described by (Hlásková et al. 2018). Based on the sieve analysis results, these authors found that the increased modification temperature of beech wood resulted in a reduced content of the smallest particles in the dust created in sanding. However, in the dust of wood modified at higher temperatures, the microscopic image analysis showed a higher content of the finest particles. The use of the laser diffraction analysis method to assess the content of the finest particles in the under-sieve fraction (containing the smallest particles) also allowed the conclusion that when milling modified pine wood, the modification temperature influences the higher content of finest particles in the resulting dust (Piernik et al. 2019).

(Mikušová et al. 2019) investigated the influence of various thermal treatment temperatures on the size distribution of wood dust created by a hand-held belt sander. Test samples were made of meranti (Shorea accuminata) wood. The untreated and thermally modified samples at temperatures of 160, 180, 200, and 220°C samples were compared using the optical and gravimetric methods. The mass proportion of the finest inhalable particles in tested wood dust was highest at the treatment temperature of 160°C. The author stated that mass proportion was not significantly influenced by thermal treatment.

The occurrence of the finest particles (≤ 10 µm) in the dust created of untreated and thermally modified wood of five species (aspen, fir, maple, ash, and poplar), was also investigated. Thermal modification of wood did not affect the amount of these particles in the air (Aro et al. 2019). (Majka et al. 2022) compared the dust from untreated beechwood to the dust from thermally modified beechwood (200°C, 3 h). The authors studied whether the thermal modification changes the particle size distributions and whether all four dust sieve fractions contain the finest particles. The wood materials were sanded with P120 paper. The dust were separated into four sieve fractions with grain sizes < 25 µm, 25–80 µm, 80–250 µm, and > 250 µm. Both types of tested dust had similar particle size distributions. Based on measurements using a laser particle sizer, the presence of particles < 10 µm in each of the four fractions was found. The authors confirmed that the sieve fractionation method has limitations, and the laser analysis method is necessary to assess the finest particles in dust correctly. The sieve method has limitations as its accuracy decreases with particles smaller than 100 µm. The results distort a mixture of particles of different specific weights, nonspherical particles (e.g. needle-shaped), prone to agglomeration particles (e.g., containing water, adhesives, susceptible to triboelectric charging), and brittle particles.

Among the examined cases, oak wood dust is characterized by the highest average share of the finest particles (of all assumed ranges, i.e. <2.5, 4 and 10 µm), which, when dispersed in the air, may pose a health risk to workers in the surroundings of workstations. This statement concerns the dust of untreated and thermally modified wood.

Generally, sanding dust from thermally modified wood generates a lower average content of potentially harmful particle fractions than sanding dust from untreated wood. It was observed for all levels of discrimination. This regularity is not confirmed only by the results of the analysis of spruce dust samples. It seems that this may be a result of (a) the generally low average content of these fractions and (b) a relatively large dispersion of the results, which may be the effect of the irregularity of the spruce dust particle shape; the irregularity in shapes worsening the accuracy of the measurement using the laser diffraction method.

The extreme temperatures were used in the thermal modification of wood, a low (160°C) and a highest (220°C), it should be assumed that the above two statements about (a) generally lower content of potentially harmful particle fractions compared to the dust generated when sanding untreated wood, and (b) there are no statistically significant differences in the average content of the finest fractions, are valid at all intermediate temperature variants used in thermomodification of woods.

Author Contributions.

Conceptualization, TR; Methodology, TR, LH, MK; Validation, TR; Formal Analysis, JM; Investigation, MK, RK, LH and MP; Resources, MK, LK and LK; Data Curation, JM; Writing – Original Draft Preparation, MS, TR, LH; Writing – Review & Editing, MS; Visualization, JM; Supervision, TR; Funding Acquisition, LH and TR.

Acknowledgments –

Aro MD, Geerts SM, French S, Cai M (2019) Particle size analysis of airborne wood dust produced from sawing thermally modified wood. European Journal of Wood and Wood Products 77:211–218. https://doi.org/10.1007/s00107-019-01385-z
Callé S, Klaba L, Thomas D, et al (2005) Influence of the size distribution and concentration on wood dust explosion: Experiments and reaction modelling. Powder Technology 157:144–148. https://doi.org/10.1016/j.powtec.2005.05.021
Dzurenda L, Orlowski K, Grzeskiewicz M (2010) Effect of thermal modification of oak wood on sawdust granularity. Drvna Industrija 61:89–94
Hlásková L, Kopecký Z, Rousek M, et al (2018) Dust emissions during sanding of thermally modified beech wood. In: Chip and Chipless Woodworking Processes. Technická univerzita vo Zvolene, Zvolen, pp 51–57
Kminiak R, Dzurenda L (2019) Impact of sycamore maple thermal treatment on a granulometric composition of chips obtained due to processing on a CNC machining mentre. Sustainability (Switzerland) 11:. https://doi.org/10.3390/su11030718
Kučerka M, Očkajová A (2018) Thermowood and granularity of abrasive wood dust. Acta Facultatis Xylologiae Zvolen res Publica Slovaca 60:43–51. https://doi.org/10.17423/afx.2018.60.2.04
Majka J, Sydor M, Pędzik M, et al (2022) Quantifying the Finest Particles in Dust Fractions Created During the Sanding of Untreated and Thermally Modified Beech Wood. Bioresources 17:7–20. https://doi.org/10.15376/biores.17.1.7-20
Marková I, Mračková E, Očkajová A, Ladomerský J (2016) Granulometry of selected wood dust species of dust from orbital sanders. Wood Research 61:983–992
Mikušová L, Očkajová A, Dado M, et al (2019) Thermal treatment’s effect on dust emission during sanding of meranti wood. BioResources 14:5316–5326. https://doi.org/10.15376/biores.14.3.5316-5326
Očkajová A, Barcík Š, Kučerka M, et al (2019) Wood dust granular analysis in the sanding process of thermally modified wood versus its density. BioResources 14:8559–8572
Očkajová A, Kučerka M, Banski A (2018a) The influence of heat treatment on granularity of sand wood dust. Chip and Chipless Woodworking Processes 11:123–130
Očkajová A, Kučerka M, Kminiak R, et al (2020a) Occupational Exposure to Dust Produced when Milling Thermally Modified Wood. IJERPH 17:1478. https://doi.org/10.3390/ijerph17051478
Očkajová A, Kučerka M, Kminiak R, Rogoziński T (2020b) Granulometric composition of chips and dust produced from the process of working thermally modified wood. Acta Facultatis Xylologiae Zvolen 62:103–111. https://doi.org/10.17423/afx.2020.62.1.09
Očkajová A, Kučerka M, Krišťák L, Igaz R (2018b) Granulometric analysis of sanding dust from selected wood species. Bioresources 13:7481–7495. https://doi.org/10.15376/biores.13.4.7481-7495
Pędzik M, Rogoziński T, Majka J, et al (2021) Fine Dust Creation during Hardwood Machine Sanding. Applied Sciences 11:6602. https://doi.org/10.3390/app11146602
Pędzik M, Stuper-Szablewska K, Sydor M, Rogoziński T (2020) Influence of Grit Size and Wood Species on the Granularity of Dust Particles during Sanding. Appl Sci 10:8165. https://doi.org/10.3390/app10228165
Pertti V, Saila J, Pentti E, Hannu V (1997) Method for improving biodegradation resistance and dimensional stability of cellulosic products
Piernik M, Rogoziński T, Krauss A, Pinkowski G (2019) The influence of the thermal modification of pine (Pinus sylvestris L.) wood on the creation of fine dust particles in plane milling: Fine dust creation in the plane milling of thermally modified pine wood. Journal of Occupational Health 61:481–488. https://doi.org/10.1002/1348-9585.12075
Rogoziński T, Chuchala D, Pędzik M, et al (2021) Influence of drying mode and feed per tooth rate on the fine dust creation in pine and beech sawing on a mini sash gang saw. Eur J Wood Prod 79:91–99. https://doi.org/10.1007/s00107-020-01608-8
Stamm AJ, Hansen LA (1937) Minimizing wood shrinkage and swelling. Effect of Heating in Various Gases. Forest Products Laboratory, Madison, Wis., USA
Sydor M, Mirski R, Stuper-Szablewska K, Rogoziński T (2021) Efficiency of machine sanding of wood. Appl Sci 6:2860. https://doi.org/10.3390/app11062860
(1995) Wood dust and formaldehyde. WHO. International Agency for Research on Cancer (IARC), Lyon, UK

No competing interests reported.

Download PDF

Journal Publication

published 30 Jul, 2023

Read the published version in European Journal of Wood and Wood Products →

Version 1

posted

You are reading this latest preprint version

The finest particles in dust after sanding untreated and thermally modified spruce, oak and meranti wood

Status:

Journal Publication

Version 1

Abstract

Figures

1 Introduction

2 Material And Methods

3 Results

4 Discussion

5 Conclussions

Declarations

Author Contributions.

Acknowledgments –

References

Additional Declarations

Status:

Journal Publication

Version 1