Frequently Asked Questions

DOHSBase Online is an online chemical substance database for occupational hygienists, safety professionals and toxicologists. The database contains over 325,000 substances with occupational exposure limits (OELs), REACH DNELs, kick-off values, GHS/CLP classifications, physico-chemical properties and measurement methods — hierarchically structured so you see the most relevant value per substance first. DOHSBase was founded in 1992 within the NVvA Working Group on Limit Values and Measurement Methods and is updated at least twice a year by registered occupational hygienists.

DOHSBase contains over 325,000 substances, including:

• 15,000+ formal occupational exposure limits (8-hour TWA, STEL, ceiling and biological limit values)
• 5,300+ REACH DNEL values
• 100,000+ kick-off values for substances without a formal OEL
• 5,500+ internationally recognised measurement methods

DOHSBase supports all types used in practice: the 8-hour time-weighted average (TWA), the short-term exposure limit (STEL, typically 15 minutes), the ceiling value (must not be exceeded at any moment) and the biological limit value (BLV, also BEI, BGW or BAT depending on jurisdiction). REACH DNELs are included alongside, and — for substances without a formal OEL — DOHSBase kick-off values are available. See the limit values overview for the full explanation.

DOHSBase publishes databases for the Netherlands, France and a pan-European edition with international limit values. The Dutch edition is the primary product; the French and European editions follow the same methodology with region-specific OEL lists.

DOHSBase is updated at least twice a year. Updates include new and revised limit values from national and international sources, REACH DNEL updates, GHS/CLP reclassifications and additions to the substance inventory.

Kick-off values are conservative numerical OEL-equivalents for substances that lack a formal occupational exposure limit. They are calculated as the 10th percentile of the existing OEL distribution within the highest GHS/CLP hazard class assigned to the substance — meaning 90% of the formal OELs for substances in the same hazard category are higher.

The kick-off methodology is an NVvA methodology: developed within the NVvA Working Group on Limit Values, published through the NVvA Newsletter (2006), and peer-reviewed by Theo Scheffers in Annals of Work Exposures and Health (2016). See the kick-off values background article for the full explanation.

Yes. The Dutch Labour Inspectorate (Nederlandse Arbeidsinspectie) has named DOHSBase kick-off values since 2012 as an acceptable source for private occupational exposure limits in its self-inspection tool for hazardous substances, alongside SER, GESTIS and COSHH. The RIVM knowledge note KU-2023-0008 (2023, commissioned by the Dutch Ministry of Social Affairs) places kick-off values at step 6 of the hierarchy of sources for private OELs.

Yes. DOHSBase contains more than 5,300 REACH DNEL values (Derived No-Effect Levels) from official REACH registration dossiers, classified by exposure route (inhalation, dermal, oral) and exposed population (workers, consumers). A DNEL is treated as an alternative OEL when no formal limit is available — see DNEL versus OEL for the hierarchy and usage rules.

Yes. DOHSBase Online includes the UTL Compliance module: a Monte Carlo simulation that tests measurement data against the Upper Tolerance Limit requirement of EN 689 (95% of workdays below the limit value with 70% statistical confidence). The module accepts log-normally distributed measurement data, runs thousands of simulations and returns a pass/fail conclusion with statistical context. See EN 689 UTL Compliance for the methodological basis.

All data is validated before publication by registered occupational hygienists on the DOHSBase team. The team includes co-founders Theo Scheffers (Honorary Member of the NVvA, EPOH board member) and Geert Wieling (registered occupational hygienist, active NVvA member), with Fenneke Linker (toxicologist) and Saskia Houben (occupational safety). See about us for the full team.

DOHSBase Online is the web database for looking up substances, OELs, classifications and measurement methods — one substance per query, hierarchically structured per tab.

DOHSBase Compare is a complementary module that compares multiple substances side-by-side on health risk via a Risk Assessment Score (RAS), calculated from a TOX index (toxicity) and a TIX index (exposure potential). Compare is suitable for ranking, prioritisation and substitution assessment.

Yes, you can create a free trial account that lets you look up ten substances. The trial gives full access to all data tabs for those substances, including OELs, classifications, kick-off values and measurement methods.

The Data Export for Stoffenmanager® transfers validated chemical safety data directly from DOHSBase Online to Stoffenmanager®, accelerating risk assessments and eliminating manual data entry. The feature is available to DOHSBase Online subscribers.

You can export verified data such as OELs (TWA, STEL, ceiling), GHS/CLP classifications, H-statements, physico-chemical properties and measurement methods — directly usable for risk inventories in Stoffenmanager®.

We’ve moved the DOHSBase application to portal.dohsbase.nl, a subdomain of our main site.

The previous address, dohsbaseonline.com, still works so existing bookmarks, email links and references in documentation continue to function. Your account, subscription and data are unchanged; you can sign in at either address with the same credentials.

For new links, bookmarks and email signatures we recommend using portal.dohsbase.nl. That is now the primary address of the application.

Install a TOTP authenticator app on your mobile device (Google Authenticator, Microsoft Authenticator, Apple Passwords, Authy or any other TOTP-compatible app), then:

1. In DOHSBase Online, go to “MY ACCOUNT” in the menu bar
2. Select “TWO-FACTOR AUTHENTICATION”
3. Scan the QR code with your authenticator app
4. Enter the 6-digit code to confirm the setup
5. Store your backup codes in a safe place

All standard TOTP (Time-based One-Time Password) authenticator apps are supported, including Google Authenticator, Microsoft Authenticator, Apple Passwords, Authy and any other TOTP-compatible authenticator. SMS verification is no longer supported due to security risks (SIM swap, unencrypted transmission).

Different authenticator apps handle device transfer differently:

• Google Authenticator: use the built-in transfer feature
• Microsoft Authenticator: sign in with your Microsoft account on the new device
• Apple Passwords: codes sync automatically via iCloud
• Authy: install Authy on the new device and sign in

Lost access to your old authenticator? Disable two-factor authentication temporarily before switching phones, or use your backup codes to re-enroll.

Use your stored backup codes to sign in and then set up a new authenticator. Lost both your authenticator and your backup codes? Contact our support team — you will need to verify your identity through additional security checks.