Building standards - ventilation guidance: research

Annex A: guidance

Please see PDF for the text below in table format.

CIBSE TM40 - 2020 Guide – Indoor air quality comparisons

Figure 2 Indoor air quality recommendations

Recommendations related to health (continued)

Pollutant:

NO₂

WHO guidelines:

• 200 μg/m³ 1-hour average
• 40 μg/m³ annual average

(WHO, 2010a)

UK regulations:

(Ambient EU and UK objective; COSHH WEL)

AD-F performance criteria:

• 288 μg/m³ 1-hour average
• 40 μg/m³ annual average

(MHCLG, 2013b)

CIBSE recommendations:

• 200 μg/m³ 1-hour average
• 40 μg/m³ annual average

Comments:

The WHO notes that there is ‘no evidence for an exposure threshold’ (WHO, 2010a). It is therefore recommended to reduce exposure levels as much as possible, rather than the guideline levels being seen as ‘safe’

Pollutant:

SO₂

WHO guidelines:

• 20 μg/m³ 24-hour mean
• 500 μg/m³ 10-minute mean

(WHO, 2006a)

UK regulations:

(Ambient EU and UK objective; COSHH WEL)

CIBSE recommendations:

• 20 μg/m³ 24-hour mean
• 500 μg/m³ 10-minute mean

Comments:

The WHO guidelines are for general air quality; the WHO has not identified SO2 as a pollutant for which specific indoor air quality guidelines are required (WHO, 2010a)

Pollutant:

PM₁₀

• 20 μg/m³ annual average
• 50 μg/m³ 24-hour average

(WHO, 2006a)

UK regulations:

(Ambient EU and UK objective; COSHH WEL on dust)

CIBSE recommendations:

• 20 μg/m³ annual mean
• 50 μg/m³ 24-hr mean

Reduce as much as possible, as no safe level is known

Comments:

The WHO guidelines (2006a) are currently under revision; publication is expected in 2020 (WHO, 2018a)

The WHO (2010) identified the need for indoor air quality guidelines on particulate matters, and concluded that their existing ones from 2006 ‘are also applicable to indoor spaces’

It also states that ‘there is little evidence to suggest a threshold below which no adverse health effects would be anticipated’ and therefore the guidelines are produced for the purpose of standard- setting on the basis of risk assessments and public health priorities, but authorities are encouraged to adopt increasingly stringent limits (WHO, 2006a)

Pollutant:

PM_2.5

• 10 μg/m³ annual average
• 25 μg/m³ 24-hour average

(WHO, 2006a)

UK regulations:

(Ambient EU and UK objective; COSHH WEL on dust)

CIBSE recommendations:

• 10 μg/m³ annual mean
• 25 μg/m³ 24-hour mean

Reduce as much as possible, as no safe level is known

Comments:

The WHO guidelines (2006a) are currently under revision; publication is expected in 2020 (WHO, 2018a)

The WHO (2010) identified the need for indoor air quality guidelines on particulate matters, and concluded that their existing ones from 2006 ‘are also applicable to indoor spaces’

It also states that ‘there is little evidence to suggest a threshold below which no adverse health effects would be anticipated’ and therefore the guidelines are produced for the purpose of standard- setting on the basis of risk assessments and public health priorities, but authorities are encouraged to adopt increasingly stringent limits (WHO, 2006a)

Pollutant:

Ultra-fine particles (< 0.1 μm in diameter)

WHO guidelines:

Currently insufficient evidence to produce guideline concentrations (WHO, 2006a)

UK regulations:

(COSHH WEL on dust)

CIBSE recommendations:

No recommended level can be proposed — project teams to remain informed of status of knowledge and guidance

Comments:

The WHO guidelines (2006a) are currently under revision; publication is expected in 2020 (WHO, 2018a)

The WHO (2010) identified the need for indoor air quality guidelines on particulate matters, and concluded that their existing ones from 2006 ‘are also applicable to indoor spaces’

It also states that ‘there is little evidence to suggest a threshold below which no adverse health effects would be anticipated’ and therefore the guidelines are produced for the purpose of standard- setting on the basis of risk assessments and public health priorities, but authorities are encouraged to adopt increasingly stringent limits (WHO, 2006a)

Pollutant:

Ozone

WHO guidelines:

• 100 μg/m³ 8-hour mean (WHO, 2006a)

UK regulations:

(Ambient EU and UK objective; COSHH WEL)

AD-F performance criterion: 100 μg/m³ (MHCLG, 2013b)

CIBSE recommendations:

100 μg/m³ 8-hour mean

Comments:

The WHO guidelines are for general air quality; in 2010 the WHO identified ozone as a pollutant for which specific indoor air quality guidelines should be recommended but found that current evidence was uncertain or not sufficient (WHO, 2010a)

Pollutant:

CO

WHO guidelines:

• 100 mg/m³ 15-min average
• 35 mg/m³ 1-hour average
• 10 mg/m³ 8-hour average
• 7 mg/m³ 24-hour average

(WHO, 2010a)

UK regulations:

(Ambient EU and UK objective; COSHH WEL, see comments)

AD-F performance criteria:

• 100 mg/m³ 15-min average
• 60 mg/m³ 30-min average
• 30 mg/m³ 1-hour average
• 10 mg/m³ 8-hour average
• For occasional exposure in nondwellings: 35 mg/m³ 8-hour average

See also comments

CIBSE recommendations:

• 100 mg/m³ 15-min average
• 60 mg/m³ 30-min average
• 30 mg/m³ 1-hour average
• 10 mg/m³ 8-hour average
• 7 mg/m³ 24-hour average
• For occasional exposure in nondwellings: 35 mg/m³ 8-hour average

Comments:

See also regulatory requirements in sections 9.2 and 9.4.7

The COSHH WEL limits are higher than AD-F; the WEL for 8-hour exposure is 23 mg/m³ and therefore lower than the AD-F for occasional 8-hour exposure, but may be present more often, as an occupational limit (HSE, 2018)

Pollutant:

Lead

WHO guidelines:

0.5 μg/m³ annual average

(WHO, 2019a)

UK regulations:

(Ambient EU and UK objective; Occupational Exposure Limit under Control of Lead at Work Regulations 2002)

0.25 μg/m³ annual mean Based on UK ambient air quality objective (Defra, 2007)

Comments:

—

Pollutant:

Formaldehyde (a VOC)

WHO guidelines:

100 μg/m³ 30-min average

(WHO, 2010a)

UK regulations:

(COSHH WEL)

AD-F: no limit except as part of TVOCs; see below

CIBSE recommendations:

100 μg/m³ 30-min average

Comments:

Consider implementing a lower target for buildings which are not yet fully fitted-out, to account for future additional emissions from fit-out elements

See guidance on insulating materials in section 9.4.4

Pollutant:

Benzene (a VOC)

WHO guidelines:

No safe level of exposure can be recommended; exposure should be reduced as much as possible (WHO, 2010a)

UK regulations:

(Ambient EU and UK objective; COSHH WEL)

CIBSE recommendations:

Exposure should be avoided, and otherwise reduced to as low a level as possible

Comments:

—

Pollutant:

1,3-butadiene (a VOC)

WHO guidelines:

Insufficient evidence to allow the production of a guideline value (WHO, 2000)

UK regulations:

(Ambient UK objective; COSHH WEL)

CIBSE recommendations:

Maximum 2.25 μg/m³ (based on UK national air quality objective)

Since no exposure guideline is currently available, project teams should remain informed should this be developed in the future; in the meantime, reduce exposure as much as possible based on the precautionary principle

Comments:

—

Pollutant:

Trichloroethylene (a VOC)

WHO guidelines:

No safe level can be determined; guidance is based on a risk estimate rather than a safe level, i.e. concentrations associated with an excess lifetime

Cancer risk of 1:10 000, 1:100 000 and 1:1 000 000 for 230 μg/m³, 23 μg/m³ and 2.3 μg/m³ respectively (WHO, 2010a)

UK regulations:

(COSHH WEL)

CIBSE recommendations:

2.3 μg/m³ and reduce as much as possible as no safe level is known

Comments:

—

Pollutant:

Tetrachloroethylene (a VOC)

WHO guidelines:

0.25 mg/m³ annual average (WHO, 2010a)

UK regulations:

(COSHH WEL)

CIBSE recommendations:

—

Comments:

—

Pollutant:

Polycyclic aromatic hydrocarbons (PAH)

WHO guidelines:

No safe level of exposure can be recommended; exposure should be reduced as much as possible (WHO, 2010a)

UK regulations:

(Ambient EU and UK objective; COSHH WEL for some individual substances)

CIBSE recommendations:

Exposure should be avoided, and otherwise reduced to as low as possible

Comments:

—

Pollutant:

Naphthalene (a VOC and a PAH)

WHO guidelines:

0.01 mg/m³ annual average (WHO, 2010a)

UK regulations:

—

CIBSE recommendations:

0.01 mg/m³ annual average

Comments:

—

Pollutant:

Microbial contamination

WHO guidelines:

No criteria for safe microbial exposure - addressed through control of humidity and ventilation (WHO, 2009a)

UK regulations:

Legionella prevention: see chapter 13

Humidity: see section 8.3

CIBSE recommendations:

No performance level - refer to regulations as well as design and operational best practice guidance

Comments:

See also chapter 8, 'Humidity'

Odours (i.e. in the case of occupant perceptions and satisfaction (not health)

Pollutant:

Odours

WHO guidelines:

Sensory comfort guidelines for a small number of substances, based on the odour detection threshold (WHO, 2000)

UK regulations:

N/A, other than through general ventilation requirements in Building Regulations Part F

CIBSE recommendations:

Investigate if this is a reported problem; if odours are linked to a known pollutant, the above limits apply

Comments:

ANSI/ ASHRAE (2001) offers possible benchmarking based on reported detection and annoyance

Indicators

Pollutant:

TVOC (as indicator)

WHO guidelines:

WHO provides guidelines for individual VOCs, not total level

UK regulations:

(COSHH WEL for some individual substances)

AD-F performance criterion: 300 μg/m³ 8-hour average

(MHCLG, 2013b)

CIBSE recommendations:

300 μg/m³ 8-hour average

This is only an indicator; if levels are found to be high, an analysis should be carried out to identify which VOCs are present and set targets for those known or suspected to present a health hazard

Comments:

In buildings that are not yet fully fitted-out, consider implementing a lower target to account for future additional emissions from fit-out elements

See Table D.2 in Annex D for examples of some commonly found in buildings

Pollutant:

CO₂ (as indicator)

WHO guidelines:

N/A

UK regulations:

(COSHH WEL = 5000 ppm for 8-hour exposure and 15 000 ppm for 15-min exposure)

(HSE, 2018)

CIBSE recommendations:

850–900 ppm (‘medium’ air quality), or 700–750ppm (‘high’ air quality); ‘medium’ is normally recommended. These are derived from BS EN 15251 air quality classes. The standard recommends differences with outdoor CO₂ levels, rather than absolute levels. Its replacement BS EN 16798-1:2019 allows higher differences (550 ppm for Class I and 800 ppm for Class II, which at 400 ppm outdoors would result in absolute levels of 950 ppm for Class I and 1200 ppm for Class II), but it is understood that these will be reviewed in the next update

Schools:

• mechanically ventilated buildings: daily average < 1000 ppm, and above 1500 ppm for no more than 20 consecutive minutes
• naturally ventilated, or hybrid system in natural mode: daily average <1500 ppm and > 2000 ppm for no more than 20 consecutive minutes, and < 1200 ppm (newbuild) or 1750 ppm (refurbishement) for the majority of the time (ESFA, 2018)

Comments:

See section 3.9 on BS indoor air quality classes

See section 9.5 on whether CO₂ should be seen as pollutant on its own rather than an indicator