Reading a Safety Data Sheet for Job Decisions

Most people open a Safety Data Sheet (SDS) at Section 1 and give up by Section 3. That is the wrong way in. An SDS is a reference, so start with the decision you have to make and go to the sections that answer it. Can this product go in that room? Will those gloves last a four-hour job? Is the booth fan enough? This is for leads, maintenance techs, shop supervisors and anyone who now picks the product, the gear or the place. It assumes you already know the 16 sections. It will not make you an industrial hygienist, who is a specialist in measuring and controlling workplace exposures. When the sheet and the job do not line up, ask for one.

What You Will Be Able to Do

• Go straight to the SDS sections that answer a job decision.
• Confirm that you have the right sheet and a current one.
• Compare air sampling results with exposure limits, including for mixtures.
• Turn Section 8 into real questions about gloves, respirators and ventilation.
• Use Section 9 numbers to judge fire, vapor and corrosion risk.
• Say what an SDS leaves out.

Start With the Decision

Find the emergency phone number in Section 1 before you need it.

Check That You Have the Right Sheet

Before you trust any of it, run three checks.

1. Match the name. OSHA requires the product identifier to link the label, the sheet and your chemical list. Near enough is not a match, because two products from one brand can have different ingredients.
2. Match the supplier. The company in Section 1 should be the one on the label.
3. Check the date. Section 16 gives the date of the last revision. A maker that learns significant new information about a hazard, or how to protect against it, has three months to add it to the sheet. A sheet in the old format, without the 16 sections in order, is a sign to ask for a current one.

If a labeled hazardous chemical shows up with no sheet, the employer must get one from the maker or importer as soon as possible. Do not start the job using the sheet for a product that looks similar.

What Sections 2 and 3 Tell You

Section 2 gives the classification, which is the hazard class and its category. In most classes, Category 1 is the most severe. Section 3 lists the hazardous ingredients. Watch for three gaps there:

Using the Exposure Limits in Section 8

Section 8 gives the limits for the ingredients, such as OSHA's Permissible Exposure Limit (PEL) and other limits the maker uses. A limit is only a ruler. It does not tell you how much is in your air. Only air sampling can do that, and the sheet cannot.

Here are three common solvents. A ppm is one part per million of air.

Look at toluene. NIOSH, the federal research agency for worker safety, recommends half of the legal limit. A PEL is what OSHA can enforce. It is not a promise that lower levels are harmless.

Mixed Exposures

Workers rarely breathe one solvent at a time. OSHA's rule, 1910.1000(d)(2), has the employer add up a mixture this way:

Mixture total = (level 1 / limit 1) + (level 2 / limit 2) + (level 3 / limit 3)

The total must not go over 1.

Worked example: A body shop samples the air in its paint mixing room. The 8-hour averages are 80 ppm toluene, 60 ppm xylene and 50 ppm MEK.

1. Toluene: 80 / 200 = 0.40.
2. Xylene: 60 / 100 = 0.60.
3. MEK: 50 / 200 = 0.25.
4. Total: 0.40 + 0.60 + 0.25 = 1.25.

Each chemical is under its own limit, and the mixture is still over. Anyone who checks them one at a time would call this room fine. The fix is to reduce the exposure, through more ventilation or a different product, and then sample again.

Turning Section 8 Into Gear

Gloves

"Wear chemical-resistant gloves" is not a decision. Under 1910.138(b), the employer has to choose hand protection based on how it performs for the task, the conditions, how long it is worn, and the hazards. A glove that works for one solvent can fail fast against another.

Respirators

Many sheets say to use a respirator if limits may be exceeded. That sentence is bigger than it looks. Under 1910.134, required respirators come with a written program, a medical evaluation, fit testing and training. Controls such as ventilation come first, and a respirator is what you use when those are not enough or while they are being put in. A dust mask does not stop solvent vapor. The program administrator picks the cartridge, not the person holding the sheet.

Ventilation

"Use with adequate ventilation" does not say how much. Adequate means that the air stays under the limits, and sampling is how you show it. Opening a door is not a ventilation plan, especially for vapors that sink to low spots.

Eyewash

If the sheet shows a corrosive, 1910.151(c) requires facilities for quick drenching or flushing of the eyes and body within the work area, for immediate emergency use. The sheet will not tell you whether your site has one. Go and look.

The employer also has to assess the workplace for PPE hazards under 1910.132(d) and certify that in writing. The SDS feeds that assessment. It does not replace it.

Section 9 Numbers That Change the Plan

Worked example: Toluene has a flash point of about 40°F, so it makes ignitable vapor in nearly any shop. One common form of xylene has a flash point of about 90°F. A crew uses a xylene cleaner in a metal shed on a 95°F day. The liquid can now be above its flash point, so the plan that worked in January does not work in July. It is the same product in a different place.

The Lower Limit Is Not a Health Limit

Toluene's lower flammable limit (LEL) is 1.1% in air, and 1.1% is 11,000 ppm.

Worked example: A gas meter at a tank opening reads 10% of the LEL for toluene. It looks low.

1. 10% of 11,000 ppm = 1,100 ppm.
2. The PEL is 200 ppm, so that is 5.5 times the legal average.
3. NIOSH's level for Immediately Dangerous to Life or Health (IDLH) is 500 ppm, so it is more than twice that too.

Air that is far too lean to burn can still be dangerous to breathe. Read fire numbers for fire and health numbers for health.

Reading Section 10 for What Happens Next

Section 10 lists conditions to avoid, incompatible materials and what the product can break down into. This matters when your task changes the chemical. Heat, sparks and even light can do it. Under 1910.252(c)(11)(ii), degreasing with chlorinated solvents has to be located so that the vapors do not reach the air around any welding. OSHA also says trichloroethylene and perchloroethylene should be kept out of air reached by the ultraviolet light of gas-shielded welding. The concern is that a welding arc can turn these vapors into much more toxic gases. Someone reading the two jobs separately would never see it. The hazard is in the combination.

What a Sheet Cannot Tell You

An SDS describes the product. It does not describe your job.

• Your task. Spraying, heating, or working in a small room can create far more exposure than brushing the product on in open air.
• Your air. The sheet gives limits, not your levels.
• Your combination. Each sheet covers one product. It will not tell you what the other three in the room do.
• Your site. It does not know where your drains, fans, eyewash or ignition sources are.
• The missing data. If a maker finds no relevant information for a sub-heading, the rule says to mark that on the sheet. That means nobody found any.

Warning: "No data available" does not mean safe. It means the sheet has no answer. Treat that hazard as unknown, and ask your safety lead before you plan around it.

A Full Decision, Start to Finish

Worked example: A school maintenance lead is asked to try a new floor stripper in a basement corridor with few windows.

The sheet did not say "no." It listed what the job needs. If the site cannot provide those things, the job waits until it can.

Common Mistakes

Check Your Understanding

1. Section 3 gives an ingredient as 10 to 30%. How should you plan?

Plan around the top of the range. The exact amount is not given, so do not assume the low number.

2. Sampling shows two solvents, each under its own PEL. Why can the room still be a problem?

OSHA has the employer add up a mixture. Each level divided by its limit can total more than 1, even when each one passes alone.

3. Section 9 lists a vapor density of 3, and you will use the product beside a floor pit. What is your concern?

Above 1, the vapor is heavier than air, so it can sink and collect in the pit. Plan for that low spot.

4. Section 8 calls for a respirator if ventilation falls short. A supervisor hands out dust masks. What is wrong?

Dust masks do not stop vapor, and required respirators need a program with medical evaluation, fit testing and training. Fix the ventilation first.

5. Section 11 says "no data available" for long-term effects. What should your plan assume?

That the hazard is unknown, not that it is absent. Control the exposure, and ask your safety lead.

Key Takeaways

• Start with your decision, and go to the sections that answer it.
• Match the name, supplier and date before you trust a sheet.
• A limit is a ruler, and only air sampling shows your exposure.
• For mixtures, add each level divided by its limit. The total must not go over 1.
• Fire numbers and health numbers are far apart, so read each for what it is.
• The sheet describes the product, so you still have to think about the task, the space and the mix.