Table 1

Investigations of exposure to CO and NO₂ in enclosed ice rinks

Study (ref No)	Type of study	Identified risk factors	Key health effects or attack rate	Biomonitoring CO, NO₂, and key findings	Author recommendations	Follow up
EpI, epidemiological investigation; EnI, environmental investigation; MIR, malfunctioning ice resurfacing machine; gIR, gasoline resurfacing machine; pIR, propane resurfacing machine; eIR, electric resurfacing machine; ppm, parts per million; ppb, parts per billion; IV, inadequate ventilation; RMIR, regular maintenance of ice resurfacing machine; ICM, install catalytic muffler; ReIR, replace with electric ice resurfacing machine; AV, adequate ventilation; ARI, NO₂-induced acute respiratory illness; Haem, NO₂ induced haemoptysis; COP, carbon monoxide poisoning; QT, qualified technican.
1	EnI or EpI	MIR, IV	COP	Range: 25–50 ppm CO	↓ Standards for indoor air quality	?

2	EnI or EpI	gIR and pIR	COP	After incident 100 ppm CO	Adjust air fuel mixture,	?
					Warm up gIR and pIR,
					Shorten resurfacings,
					↓ No of resurfacings

3	EnI or medical reports	MIR, IV	ARI	After incident 3 ppm NO₂	Long exhaust pipe,	?
				Temperature inversion maintained high	RMIR, ICM, AV
				↑ Exposure time,
				↑ Probability of poisoning

4	EnI/EpI	MIR, IV	ARI 69%, Haem 20%	After incident 3–4 ppm NO₂	Routine monitoring	?

5	EnI or clinical investigation	MIR, IV	COP	After incident 100 ppm CO	RMIR, AV, ReIR,	After AV 23 ppm CO
			Rink employees		After warning signs,	After ReIR 1 ppm CO
					Routine monitoring,
					↓ Standards for indoor air quality

6	EnI or EpI	MIR	COP	After incident 100 ppm CO	AV, RMIR	After ICM, RMIR 5–10 ppm CO
					QT

7	EnI or clinical investigation	MIR, IV	ARI	After incident 4 ppm NO₂	?	?

8	EnI or EpI	MIR, IV	COP, Team A 100%,	After incident 47 ppm CO	AV	?
			Team B 83%
			Medical personnel 100%
			Referees 50%

9	EnI or EpI	MpIR, IV	ARI 55.6%	After incident 1250 ppb NO₂	AV, ReIR,	?
				↑ Risk of pulmonary symptoms with ↑ time on ice	Routine monitoring
					Set guidelines for air quality

10	EnI or EpI	MIR, IV	NO₂ induced severe symptoms 82%,	After incident range: 0.5–1 ppm NO₂	AV, ReIR, RMIR	?
			Mild symptoms 100%

11	EnI or EpI	MIR, IV	COP 54% players,	After incident 40 ppm CO	?	?
			Coaches, teachers

12	EnI or clinical investigation	MIR, IV	ARI 48% players	After incident 150 ppm CO	AV, ReIR, RMIR	?
			Spectators	After incident 1.5 ppm NO₂	Education of staff

13	EnI 20 rinks	MIR, IV	?	73 ppm CO	RMIR, ReIR, AV	?
				0.1 ppm NO₂
				↑ No of resurfacings
				↑ CO
				Rinks varied in CO

14	EnI	MIR, IV	?	4240 ppb NO₂	Lower NO₂	?
				1 hour maximal
				Increased NO₂

15	EnI 332 rinks	MIR, IV	?	40% rinks ↑ NO₂	ReIR	?

16	EnI 70 rinks	MIR	?	Indoor NO₂ 10× v outdoor	Long exhaust pipe	?
				60% Exceeded standards	AV,
				1 hour standard	↓No of resurfacings
				40% Exceeded standards
				1 week average standard
				1 week average 180 ppb NO₂

17	EnI 70 rinks	MIR	?	Outdoor rink = 16.3 ppb NO₂	Set guidelines for air quality	?
				Indoor rink = 169.5 ppb NO₂	AV, ReIR
				Indoor NO₂ 10× v outdoor
				NO₂ higher in rinks with IV

18	EnI or clinical investigation	MIR, IV	↑ COHb	Range: 55–65 ppm CO	RMIR, QT	?
				Rink employees	Fresh air supply to inside rink
					Direct exhaust link from garage to outside

19	EnI seven rinks	MIR, IV	?	Range: 3–57 ppm CO	Shorten resurfacings,	?
				Ventilation system not in operation during resurfacings	AV, ReIR, RMIR
					Routine monitoring

20	EnI or EpI	MIR	?	50% of rinks exceeded 25 ppm CO,	Routine monitoring	?
				Range: 25–206 ppm CO,	QT, AV
				Ventilation system not in operation during resurfacings

21	EnI six rinks	gIR and pIR, IV	?	gIR range: 157–304 ppm CO	ICM, AV, ReIR	After ICM
				pIR range: 75–175 ppm CO		gIR range: 4–110 ppm CO
						pIR range: 0–105 ppm CO

22	EpI	Tobacco smoke	?	1110–1700 ppm CO₂	?	?
				237 ppb NO₂

23	EnI or clinical investigation	MIR	ARI	Increased NO₂	Corticosteroid treatment	Condition improved

24	EnI four rinks	MIR, IV	?	Range: 5–110 ppm CO	AV, ReIR, ICM, RMIR,	?
				22.5 ppm caused various CO symptoms	Warm up machine,
					Shorten resurfacings,
					Open doors of rink,
					During resurfacings, QT,
					Routine monitoring

25	EnI six rinks	MIR	?	Range: 4–117 ppm CO	1 hour maximal	?
				Range: 342–2729 ppb NO₂	Allowable 20 ppm CO and 25 ppb NO₂
				Outdoor = 37 ppb NO₂

26	EnI	MIR	?	1 week average	AV, ReIR,	Engineering controls: AV ↓ NO₂ 65%
				pIR: 206 ppb NO₂	ICM, RMIR
				gIR: 132 ppb NO₂	Routine monitoring
				eIR: 37 ppb NO₂

27	Exposure-absoption	?	?	Linear exposure-absoption relation	↓ CO in rinks	?

28	Exposure-absoption 10 rinks	MIR	?	Range: 1.6–131.5 ppm CO	CO standard of 20 ppm for 90 minutes in rinks	?
				↑ 10 ppm CO = ↑ COHb 1%

29	EnI	MIR, IV	?	Increased CO	AV, long exhaust pipe	?
					RMIR, ICM, QT
					Open doors of rink during resurfacings,
					Warm up machine,
					Flexible exhaust hose with direct link to outside

30	EnI	MIR	?	1 hour average	↑ CO gIR	?
				17–29 ppm CO	↑ NO₂ pIR
				0.14–3.96 ppm NO₂

31	EnI	MIR	?	23% Exceeded standards	Enforce regulations	?

32	EnI	MIR, IV	?	Range: 50–100 ppm CO	Routine monitoring	After RMIR, AV 2–3 ppm CO

33	EnI or EpI six rinks	MIR, IV	5×COHb	82% Exceeded standards	RMIR, AV, ReIR	?
				Range: 23–90 ppm CO