The most popular group of positive pressure ventilation fans has been subject to regulations governing pollution from internal combustion engines across the European Union since 2002. The laws refer to spark-ignition combustion engines with a power of up to 19 kW for non-road usage. In 2016, currently applicable Stage V laws were enacted, and have been in full force and effect since 2019. The provisions are set out in Regulation (EU) 1628/2016. Under the regulation, engines applied in rescue positive pressure ventilation fans are placed in category NRS which includes SI engines having a reference power that is less than 56 kW, which are not intended for use in in handheld machinery (Table 1). SI engines with a power above 56 kW must meet emission standards for category NRE engines.

Stage V emission limits for engines in non-road mobile machinery (category NRE) are shown in Table 2. These standards are applicable to CI engines from 0 to 56 kW and to all types of engines above 56 kW.

Based on the summary of internal combustion engines (Table 3) applied in fans, and the European type-approval tests (Table 1 and Table 2) it can be noted that not all engine categories refer to fans. Category NRS-vr/vi-1a engines do not refer to fans used in rescue operations because, according the results of studies performed by Kaczmarzyk et al., (2022) they work at maximum power levels in real-life operation conditions ^[2], and the category concerns a test for intermediate speed applications. The right category for the engines of fans used in rescue operations in this power and displacement range is NRS-vr/vi-1b, which is tested for rated speed applications. Moreover, categories NRS-v-2a and NRS-v-2b for engines having power in the range of 19 kW to 30 kW and displacement below or above 1000 cm³ are also unusual, as no positive pressure ventilation fans with combustion engines with such power range have been identified. Two out of all the structures available on the European market are not classified as category NRS engines, but as category NRE engines, with a power above 56 kW intended for non-road machinery. The categories listed in Table 2 are intended for low-power CI engines with a power of up to 56 kW. However, as regards this power range, only fans with SI engines belonging to the NRS category are available on the European market. Categories covering both CI and SI engines are demonstrated further in Table 2. Positive pressure ventilation fans with engines with a power above 92 kW have also not been found, and thus, as regards NRE engines, only category NRE-v/c-5 engines, characterized by a power range of 56 kW to 130 kW, can be discussed in the context of positive pressure ventilation fans.

Table 3. Mobile positive pressure ventilation fans with internal combustion power units available on the European market.

Brand	Fan Model	Engine Model	Displacement, cm3	Engine Power, kW	Engine Type	Literature Source
Ramfan	GX 200 L/GX 200	Honda GXH50	49	1.6	SI	[3]
Ramfan	GF 165	Honda GX160	163	3.6	SI	[3]
Ramfan	GX 310	Honda GX160	163	3.6	SI	[3]
Ramfan	GX350	Honda GX200	196	4.1	SI	[3]
Ramfan	GX400	Honda GX200	196	4.1	SI	[3]
Ramfan	GX500	Honda GX270	270	6.3	SI	[3]
Ramfan	GX600	Briggs & Stratton Vanguard V-Twin OHV mod.35	570	13.4	SI	[3]
Ramfan	VX700	Honda GX630	688	17	SI	[3]
Ramfan	GF 164 SE	Honda GC160	160	3.4	SI	[3]
Rosenbauer	Fanergy V16 513020	Briggs & Stratton 6.5 KM	420	4.41	SI	[4]
Rosenbauer	Fanergy V16 513022	Briggs & Stratton 6.5 KM	420	4.41	SI	[4]
Rosenbauer	Fanergy V22	Briggs & Stratton 6.5 KM	420	4.41	SI	[4]
Rosenbauer	Fanergy XL35	BMW 50 kW boxer type	850	50	SI	[4]
Leader	MT 215 L NEO	Honda GXH50	49	1.47	SI	[5]
Leader	MT 225 NEO	Honda GX120	118	2.21	SI	[5]
Leader	MT 236 NEO	Honda GX160	163	2.94	SI	[5]
Leader	MT 240 NEO	Honda GX200	196	3.68	SI	[5]
Leader	MT 245	Honda GX200	196	3.68	SI	[5]
Leader	MT 280	Honda GX390	389	0.74	SI	[5]
Leader	MT 296	Briggs & Stratton -Vanguard	479	11.77	SI	[5]
Leader	Easy 2000	Honda GX630	688	14.71	SI	[5]
Leader	Easy 4000	BMW	1170	84.58	SI	[5]
Alusteel	Kobra H34	Honda Gx160	163	3.4	SI	[6]
Fogo	Fogo MW 22	Briggs & Stration 6.0 KM	420	4.4	SI	[7]
Alusteel	Skorpion MAXI	Honda GX 160	163	3.4	SI	[6]
Pavliš	PH VP 450	Honda GX 200	196	4.1	SI	[8]
Pavliš	PH VP 600	Honda GX 270	270	6.3	SI	[8]
Rosenbauer	Fanergy XL63	Deutz 92 kW	3620	92	CI	[4]

Liberal European Union laws governing emissions from small non-road engines cover around 90% of fans available for sale on the European market. The provisions for fans with engines having a power of up to 19 kW allow CO emissions at the level of 610 g/kWh and HC + NOx emissions at the level of 8 g/kWh. More stringent emission limits are applicable to engines having higher power values (Figure 1). As regards fans with engines having a power with a range of 30 kW to 56 kW, accounting for a 3% market share in Europe, the allowable CO and HC + NOx emissions are lower by 99.3% and 66.2%, respectively (4.4 g/kWh and 2.7 g/kWh). The remaining 7% of the European market is taken by category NRE engines, which are not classified as category NRS, intended for higher-power drive units, notwithstanding the type of fuel or engine (SI and CI). Fans equipped with such engines are subject to the analysis of a greater number of air pollutants, and the set limits are relatively rigorous.

Assuming that internal combustion engines applied in ventilators are operated at maximum power ^[2], the values of exhaust gas emissions per hour can be estimated on the basis of engine power and allowable emission limits (Figure 2). It can be noted that low-power fan engines (between 0.7 kW and 17 kW), which are less technologically advanced, are characterized by a higher hourly pollutant emission than engines having substantially higher power (between 50 kW and 92 kW). An hour of operation of an engine with a power ranging from 0.7 kW to 17 kW may produce CO emissions at the level of 427 g/h to 10,370 g/h, while for engines having a higher power, between 50 kW and 92 kW, CO emissions should fall within the range of 220 g/h to 460 g/h. On the other hand, the HC + NOx emission increases with the engine power for units with a power from 0.7 kW to 17 kW in the range from 5.6 g/h to 136 g/h. Later, for the power from 50 kW to 85 kW, it decreases (from 135 g/h to 50 g/h), and then for the power of 92 kW, it starts to increase to 54 kW. The reduction of HC + NO_x emissions for engines above 17 kW is not as large as the reduction of CO emissions for engines of the same power. For example, engines with a power of 85 kW to 92 kW may have HC + NO_x emissions of 50 g/h to 54 g/h, as are engines of another 6.3 kW category, which may emit HC + NO_x at the level of 50.4 g/h. For comparison, the permissible CO emission from these engines is from 425 g/h to 460 g/h (engines with power from 85 kW to 92 kW) and 2196 g/h for engines with a power of 6.3 kW. Based on the analysis, it can be concluded that the use of fans with higher-power engines, preferably above 19 kW, is more favorable in terms of air pollution as engines exceeding this power value belong to categories which are subject to relatively stringent emission limits. The assumptions are based on maximum emission values allowable during type-approval tests. According to the results of studies conducted by Warguła et al. in 2022, small engines SI, e.g., with a power of around 10 kW, are characterized by emission levels in type-approval tests which are close to the maximum allowable values. The research included engines with a classic carburetor fuel supply system (the most popular ones on the market) and the most innovative ones with electronically controlled carburetors, and they were characterized by CO emissions at the level of 408 g/kWh to 561 g/kWh and HC + NO_x emission of 3.90 g/kWh to 4.53 g/kWh, respectively, compared with emission levels set in the European Union, namely CO 610 g/kWh and HC + NO_x 8 g/kWh ^[1]. It should be borne in mind that along with the progressing wear and tear, engines are characterized by a greater loss of fuel dosage control precision and a higher probability that larger volumes of engine lubricating oil will be consumed, which might result in increased air pollution and in exceeding the emission limits applicable in type-approval tests.