SBM 2024 Reference Values

SBM-2024 – Supplement to the Standard of Building Biology Testing Methods

Building Biology Reference Values for Sleeping Areas

Building biology reference values are precautionary values. They relate to sleeping areas, which are a particularly sensitive regeneration period for humans and the associated long-term risks. They are based on the current building biology experience and knowledge and are oriented towards what is achievable. Furthermore, scientific studies and other recommendations for evaluation are considered. The focus of building biology measurement technology is on the professional detection, minimization, and avoidance of critical environmental influences in buildings within the individually feasible framework. The aim is to identify, locate, and assess the sources of anomalies while taking all standard points into account and through a competent compilation of the many diagnostic options, in order to create as stress-free and nature-oriented a living environment as possible.

Unremarkable values offer the highest level of precaution. They correspond to natural environmental standards or the frequently encountered and almost unavoidable minimum level of civilizational influences.

Weakly noticeable means that improvements should be implemented whenever possible, with particular consideration for sensitive or sick individuals.

Strongly noticeable is no longer acceptable from a building biology perspective. Action is required. Renovations should be carried out soon. Numerous case studies often point to biological effects and health problems, as do scientific studies.

Extremely noticeable values require consistent and immediate renovation. Here, international reference values and recommendations for indoor and workplace environments are sometimes reached or exceeded.

If multiple anomalies occur at individual or different standard points, the overall assessment should be more critical. In principle and overall, it applies:
Every risk reduction should be pursued. Reference values are guidelines. The measure is nature.

The small print in the closing lines of each building biology standard point serves as comparative orientation, e.g., with legally binding limit values or other reference values, recommendations, and research results, or natural standards.

A. Fields, Waves, Radiation

1. Electrical Alternating Fields (Low Frequency)

The following reference values apply to low-frequency electrical alternating fields in sleeping areas. The values include earth-based field strength, body voltage, and potential-free field strength:

Values are applicable for frequencies up to and around 50 Hz; higher frequencies and significant overtones should be assessed more critically.

DIN/VDE 0848: Work 20,000 V/m, Population 7000 V/m; BImSchV: 5000 V/m; TCO: 10 V/m; US Congress/EPA: 10 V/m; Childhood leukemia studies: 10 V/m; Studies on oxidative stress, formation of free radicals, melatonin suppression: 20 V/m; BUND: 0.5 V/m; Nature: < 0.0001 V/m.

2. Magnetic Alternating Fields (Low Frequency)

The following reference values apply to low-frequency magnetic alternating fields in sleeping areas. The values include magnetic flux density in nanotesla (nT):

Values are applicable for frequencies up to and around 50 Hz; higher frequencies and significant overtones should be assessed more critically.
Power frequency (50 Hz) and railway frequency (16.7 Hz) are recorded separately.

In case of significant temporal field fluctuations, the 95th percentile derived from long-term recordings—especially overnight—should be used for evaluation.

DIN/VDE 0848: Work 5,000,000 nT, Population 400,000 nT; BImSchV: 100,000 nT; Switzerland: 1000 nT; WHO/IARC: 300-400 nT “potentially carcinogenic”;
TCO: 200 nT; US Congress/EPA: 200 nT; DIN 0107 (EEG): 200 nT; BioInitiative: 100 nT; BUND: 10 nT; Nature: < 0.0002 nT.

3. Electromagnetic Waves (High Frequency)

The following reference values apply to high-frequency electromagnetic waves in sleeping areas. The values include radiation density in microwatts per square meter (μW/m²):

Values apply to individual radio services, e.g., GSM (D-/E-networks), UMTS, TETRA, LTE, WiMAX, radio, television, WLAN, DECT, Bluetooth… Values refer to peak levels. Guidelines do not apply to rotating radar.

More critical radio waves, such as pulsed or periodic signals (mobile GSM, TETRA, DECT, WLAN, digital broadcasting…) and broadband techniques with pulsed components/structures (UMTS, LTE…) should be assessed more rigorously in cases of higher anomalies compared to less critical, unpulsed or non-periodic signals (FM, short, medium, longwave, analog broadcasting…) which can be evaluated more generously in cases of weaker anomalies.

Former building biology radio wave reference values SBM-2003: pulsed < 0.1 none, 0.1-5 weak, 5-100 strong, > 100 μW/m² extreme anomaly; unpulsed < 1 none, 1-50 weak, 50-1000 strong, > 1000 μW/m² extreme anomaly.

DIN/VDE 0848: Work up to 100,000,000 μW/m², Population up to 10,000,000 μW/m²; BImSchV: up to 10,000,000 μW/m²; Mobile communications: Switzerland up to 100,000 μW/m²;
Salzburg Resolution / Medical Association 1000 μW/m²; BioInitiative 1000 μW/m² outside; EU Parliament STOA 100 μW/m²; Salzburg 10 μW/m² outside, 1 μW/m² inside;
EEG, immune disturbance: 1000 μW/m²; Mobile phone function: < 0.001 μW/m²; Nature: < 0.000001 μW/m².

4. Electric Static Fields (Electrostatics)

The following reference values apply to electric static fields in sleeping areas. The values include surface voltage in volts (V) and discharge time in seconds (s):

Values apply to conspicuous materials and devices in close proximity to the body and/or for room-dominating surfaces at approximately 50% relative humidity.

TCO: 500 V; Damage to electronics, computer components: from 100 V; painful shocks, sparks: from 2000-3000 V; synthetic materials, plastic coatings: up to 10,000 V; plastic floors, laminates: up to 20,000 V; CRT screens: up to 30,000 V; Nature: < 100 V.

B. Indoor Pollutants, Contaminants, and Room Climate

1. Formaldehyde and Other Gaseous Pollutants

The following reference values apply to formaldehyde measured in micrograms per cubic meter (μg/m³):

Values apply to the sum of all volatile compounds (TVOC) in the indoor air.

Allergic, irritating, or odor-intensive individual substances or substance groups should be assessed more critically, especially for particularly hazardous or carcinogenic air pollutants such as benzene, naphthalene, cresols, styrene…

For individual assessments, see ‘AGÖF-Orientierungswerte für flüchtige organische Verbindungen in der Raumluft’ (2013).

Umweltbundesamt: 300 μg/m³; Seifert BGA target value: 200-300 μg/m³; Molhave: 200 μg/m³; AGÖF normal value a) Sum: 360 μg/m³, b) Individual substances (examples): Acetaldehyde 20 μg/m³, Acetone 42 μg/m³, Benzene 1 μg/m³, Ethylbenzene 1 μg/m³, Naphthalene < 1 μg/m³, Phenol < 1 μg/m³, Styrene 1 μg/m³, Toluene 7 μg/m³, m,p-Xylene 3 μg/m³, Alpha-Pinene 4 μg/m³; Delta-3-Carene 1 μg/m³, Limonene 4 μg/m³; Nature: < 10 μg/m³.

For the assessment of odor-intensive substances, see AGÖF guidelines ‘Odors in Indoor Spaces’ (2013).

2. Solvents and Other Volatile Organic Compounds

The following reference values apply to solvents measured in micrograms per cubic meter (μg/m³):

Values apply to the sum of all volatile compounds (TVOC) in the indoor air.

Allergic, irritating, or odor-intensive individual substances or substance groups should be assessed more critically, especially for particularly hazardous or carcinogenic air pollutants such as benzene, naphthalene, cresols, styrene…

For individual assessments, see ‘AGÖF-Orientierungswerte für flüchtige organische Verbindungen in der Raumluft’ (2013).

3. Pesticides and Other Semi-volatile Pollutants

The following reference values apply to pesticides measured in nanograms per cubic meter (ng/m³) and other materials:

Values refer to the sum of all volatile compounds and apply to secondary contaminations, not for primary contaminations (i.e., not for directly vacuumed treated sources, surfaces, and materials).

PCP prohibition regulation: Material 5 mg/kg; PCP guideline: Air 1000 ng/m³, target value 100 ng/m²; ARGE-Bau: Air 100 ng/m³, Dust 1 mg/kg;
PCB guideline target: 300 ng/m³; PCB remediation target NRW: 10 ng/m³; acute health hazard: 3000 ng/m³; special disposal: 50 mg/kg.
AGÖF normal values for dust (examples): PCP 0.3 mg/kg, Lindan 0.1 mg/kg, Permethrin 0.5 mg/kg, Chlorpyrifos 0.1 mg/kg, DDT/DDD/DDE < 0.1 mg/kg,
Dichlofluanid 0.1 mg/kg, Tolylfluanid < 0.1 mg/kg, TCEP 0.5 mg/kg, PAK Benzo-(a)-pyrene < 0.2 mg/kg, DEHP 400 mg/kg.

For further assessment assistance, see ‘AGÖF-Orientierungswerte für mittel- und schwerflüchtige Stoffe im Hausstaub’ (2004), currently being revised.

4. Heavy Metals and Other Related Pollutants

There are currently no building biology reference values for heavy metals.
For assessment assistance, see ‘AGÖF-Orientierungswerte für mittel- und schwerflüchtige Stoffe im Hausstaub’ (2004).

5. Particles and Fibers (Fine Dust, Nanoparticles, Asbestos, Mineral Fibers…)

The concentration of particles, fibers, or dust should be below the usual uncontaminated background levels found outdoors.
Asbestos should not be detectable in indoor air, on surfaces, or in dust, or only minimally.

Former building biology asbestos air reference values SBM-2000: < 100 none, 100-200 weak, 200-500 strong, > 500/m³ extreme anomaly.
Asbestos fibers in air – BGA: 500-1000/m³; TRGS target value: 500/m³; EU: 400/m³; WHO: 200/m³; outdoor air: 50-150/m³; clean air regions: 20/m³.

Particles in air – (Annual Average) BImSchV: 40 μg/m³, EU: 50 μg/m³ (< 10 μm), 25 μg/m³ (< 2.5 μm);
EPA: 25 μg/m³ (< 2.5 μg/m³); VDI: 75 μg/m³; Zugspitze: 5-10 μg/m³; Country: 20-30 μg/m³; City: 30-100 μg/m³; Room with cigarette smoke: > 1000 μg/m³; Smog Alarm Level 1: 800 μg/m³.

6. Room Climate (Temperature, Humidity, Carbon Dioxide, Air Ions, Air Exchange, Odors…)

6.1 Relative Humidity

The following reference values apply to relative humidity measured in percentage (%):

6.2 Carbon Dioxide

The following reference values apply to carbon dioxide measured in parts per million (ppm):

MAK: 5000 ppm; DIN: 1500 ppm; Umweltbundesamt: 1000 ppm; USA (workplaces/classrooms): 1000 ppm;
Unventilated bedrooms in the morning or classrooms after a lesson: 2000-4000 ppm;
Nature 2015: 400 ppm, 1985: 330 ppm; annual increase: 1-2 ppm.

6.3 Air Ions

The following reference values apply to air ions measured per cubic centimeter (cm³):

Note: High air ion levels indoors may indicate radon presence.

Coastal areas: > 2000/cm³; clean air regions: ~ 1000/cm³; countryside: < 800/cm³; city: < 700/cm³;
industrial areas/traffic: < 500/cm³; room with electrostatics: < 300/cm³; room with cigarette smoke: < 200/cm³;
smog: < 50/cm³; steady decline in air ion levels over the past decades.

6.4 Air Electricity

The following reference values apply to air electricity measured in volts per meter (V/m):

DIN/VDE 0848: Work 40,000 V/m, Population 10,000 V/m; Nature: ~ 50-200 V/m, Föhn: ~ 1000-2000 V/m, Thunderstorms: ~ 5000-10,000 V/m.

C. Fungi, Bacteria, Allergens

1. Mold and Their Spores and Metabolites

In indoor spaces, there must be no visible mold infestations or contamination with mold spores or mold metabolites.
The mold counts in the air, on surfaces, in household dust, in cavities, in materials… should be lower than those outdoors or in uncontaminated comparison rooms.

The types of molds indoors should not differ significantly from those outdoors or in uncontaminated comparison rooms.
Particularly critical molds, such as toxin-producing, allergenic, or those growing at 37 °C body temperature, must not be detectable or only minimally present.
Permanently elevated material and air humidity, as well as cool surface temperatures, should be avoided as they provide the basis for mold growth.

Any anomaly, suspicion, or indication of microbial contamination must be investigated, including: discoloration and stains,
typical microorganisms odors, moisture-indicative molds, construction and moisture damage, problem constructions, hygiene aspects,
above-average entries from outside, old damage, building history, site inspection, resident illnesses, environmental medical results…

Orienting building biology evaluation aids for examinations of air, surfaces, dust, MVOC, water activity, moisture…
and further details in the measurement technical conditions, explanations, and supplements should be considered.

Detailed evaluations and information: Federal Environment Agency ‘Mold Guideline’ and ‘Mold Remediation Guideline’.

Former building biology mold reference values SBM-1998 to SBM-2003 (using YM Building Biology Agar and incubation at 20-24 °C, colony-forming units CFU):
Air < 200/m³ none, 200-500 weak, 500-1000 strong, > 1000/m³ extreme anomaly (indications for indoor air at relatively low reference values of outdoor air under 500/m³);
Surfaces < 20/dm² none, 20-50 weak, 50-100 strong, > 100/dm² extreme anomaly (indications for smooth surfaces under everyday, regularly cleaned conditions).

Mold in indoor air – WHO: Pathogenic and toxic molds are not acceptable in indoor air; from 50/m³ of one mold species, sources should be sought;
up to 500/m³, a mixture of commonly occurring environmental species (e.g., Cladosporium) should be present.
Senkpiel and Ohgke: Indoor concentrations that exceed outdoor air by more than 100/m³ indicate contamination.
EU statistics for housing (CEC, Commission of European Communities): < 50/m³ very low, < 200/m³ low, < 1000/m³ medium,
< 10,000/m³ high, > 10,000/m³ very high.
US OSHA (United States Occupational Safety and Health Administration): > 1000/m³ = contamination/microbial damage.

AIHA (American Industrial Hygiene Association): > 1000/m³ = “atypical” situation, indoor concentration significantly above outdoor air = indoor source present.
Netherlands (Occupational Health Association): > 10,000/m³ mixed or > 500/m³ of a potentially pathogenic species = health hazard.
Finland (Ministry of Health): < 500/m³ in winter, < 2500/m³ in summer = maximum in apartments.

2. Yeast Fungi and Their Metabolites

Yeast fungi should not be detectable in the air, on surfaces, and materials or in bedding, laundry, hygiene, bathroom, kitchen, and food areas or only minimally.
This specifically applies to health-critical yeasts like Candida or Cryptococcus.

3. Bacteria and Their Metabolites

Bacterial counts in the air should be at or below those of outdoor air or uncontaminated comparison rooms.
Particularly critical bacterial species, such as certain Pseudomonas, Legionella, Actinomycetes…, should not be detectable in houses,
either in the air or on materials, in drinking water, or in hygiene, bathroom, and kitchen areas.
Every suspicion or indication must be investigated: high material moisture, moisture damage, hygiene and fecal issues,
bacteria-typical odors… In mold investigations, bacteria should be included and vice versa, as they often occur together.

4. House Dust Mites and Other Allergens

There are currently no reference values for house dust mites and allergens.
The standard of building biology measurement technology and these reference values for sleeping areas include the complementary conditions,
explanations, and supplements, which describe the measurement or analytical procedures in more detail and point out further first orienting reference proposals.

Since the building biology reference values are primarily based on long-standing experience, they are (still) not available for all standard points and are regularly supplemented and updated according to new findings.

Even in workplaces and especially in sensitive areas where we stay for long periods, all building biology loads should be kept as low as possible.
The fundamental building biology principles also apply in workplaces and beyond: every risk reduction should be pursued, with feasibility in focus.
For the assessment of work areas, various regulations, recommendations, and findings could be taken into account,
for example, TCO or US Congress/EPA (low-frequency fields, electrostatics), BioInitiative Working Group, EU Parliament STOA or BUND (high-frequency radio waves),
EU, WHO, or Federal Office for Radiation Protection (radioactivity, radon), AGÖF (pollutants)… also UBA (mold, pollutants, carbon dioxide…), VDI (pollutants), ARGE-Bau (pesticides),
LGA Baden-Württemberg (mold)…

This three-part original standard has been a guiding principle and basis for building biology measurement and preventive assessment since 1992 and is now international.
The association for building biology VB, founded in 2002, uses the standard along with the associated reference values and conditions as its working basis.

The standard, along with reference values and conditions, was developed from 1987 to 1992 by BAUBIOLOGIE MAES at the request and with the support of the Institute for Building Biology + Sustainability IBN.
Colleagues and doctors contributed to its creation. It was first published in May 1992. The standard, reference values, and conditions have been continuously updated and shaped since 1999
by experienced building biology experts with the support of independent scientists from the fields of physics, chemistry, biology, architecture, laboratories, environmental medicine,
and other experts. This current SBM-2024 is the 8th new edition, presented in March 2024.