Bulk VS Air Samples

Asbestos testing usually falls into two categories: bulk sample and air sample testing.

Whether it’s bulk samples or air samples, the goal of testing is to find the number of asbestos fibers in your sample.

For testing methods, we typically use Polarized Light Microscopy (PLM) for the bulk samples, and Phase Contrast Microscopy (PCM) for air samples.

Bulk Sampling Air Sampling
Testing solid chunks of building material

80% of the samples collected are bulk.

Bulk sampling allows you to test for asbestos in any of the solid materials in the building to find if there is any Asbestos Contaminated Material (ACM). ACM is a specific industry term, so it’s an acronym worth knowing.

PLM Testing

We analyze bulk samples using Polarized Light Microscopy (PLM).

If the polarized light microscopy fails, then Transmission Electron Microscopy (TEM) will be required.

The shortest turnaround time available for TEM is 24 hours.

If we determine that your sample requires TEM testing, we’ll call you immediately to let you know.

Testing indoor air

Air sampling is used to find asbestos that might be floating in the air.

The majority of air tests are for:

  • Type 3 asbestos removal
  • People who are concerned about the quality of their indoor air

PCM Testing

We analyze air samples using Phase Contrast Microscopy (PCM).

Air samples are collected by running air through a filter contained within a cassette.

The main problem we find with air sampling is receiving a cassette overloaded with dirt and contaminants.

The air test has to be run in a clean, dry area. The pump opening should be facing down, 5-6 feet off of the ground.

How To Collect A Bulk Sample – The Right Way

The basic steps to collecting a bulk sample are:

  1. Use personal protective equipment (including breathing masks, safety glasses, and gloves).
  2. Collect the material, put it in a Ziploc bag and seal.
  3. Label the Ziploc bag. (ex: “B1 = living room ceiling – popcorn ceiling”).
  4. Place all Ziploc bags in one larger Ziploc bag and label it with the address where the sample was taken.

Bulk Sample Examples

A small piece of solid building material is required for bulk sampling, typically the size of a dime or the tip of your pinky finger. The most common building materials where asbestos is found are:

Type How to collect it
Drywall Compound Take a sample from a wall corner where drywall mud is most concentrated.
Vinyl Floor Tiles (VCT Floor Tiles) Pick a corner and use a hook-knife or small prybar to cut off a small piece.
Linoleum Flooring Use a utility knife to cut off a small piece from the corner.
Silicone Around Windows and Sliding Doors Use a utility knife. Cut once on the window side, and once along the trim side to get a small piece (an inch long works great).
Textured Popcorn Ceiling You’ll want to avoid just scraping the ceiling because the popcorn texture will break into pieces and make a mess (remember it might also be contaminated with asbestos).

Instead, stick a 6-inch piece of duct tape to the ceiling. Using a trowel you can break off the popcorn-texture that the duct tape is covering. The texture will stick to the duct-tape, and then you can pull it off without a mess. Store your piece of tape in a Ziploc and it’s ready for delivery.

Textured Walls Use a knife to cut a piece off the wall. The entire wall will be textured, so you don’t have to only cut from the corner.
Plaster Use a knife to cut a piece off the wall, or you can use a hammer on the outside corner to break off a piece.
Thermal Insulation Around Boiler Use a utility knife to cut off a 2×2 square (inches), and put some tape on the hole you just made to protect the integrity of your insulation. The size of the sample should be around 2×2 inches.
Attic and Wall Insulation Use a utility knife to cut off a 2×2 inch square.
Roofing Materials On a flat roof, there may be asbestos in the tar, or in the paper underneath.

On a cedar-shakes shingle roof, most of them have asbestos in the paper barrier underneath the shingles.

On asphalt shingles, you have to test the paper underneath the shingle for asbestos. Usually there isn’t asbestos in the shingle itself.

Get Your Asbestos Sample Results In As Little As 3 Hours

Taking Discrete
Bulk Samples

If you or someone else is living in a house where samples need collecting, look for a discrete area to retrieve the sample, such as:

  • Behind the stove
  • Behind the fridge
  • Behind the toilet
  • In a closet

Anywhere that won’t be seen is the best place for a sample when someone is still living in the building.

Use safety gear when collecting the sample and place it in a plastic Ziploc bag, labelling each bag as you go.

Bulk Samples

Here’s an example of how you might label your bulk samples:

  • B1 = Living room ceiling – popcorn ceiling
  • B2 = Dining room corner – drywall compound
  • B3 = Bathroom floor tiles – linoleum

How Many Samples Do I Need?

Square Footage Of Surface Samples Required
Less than 968 sq. ft. minimum 3 samples
968-4,843 sq. ft. minimum 5 samples
4,843+ sq. ft. minimum 7 samples

Once the samples are labeled and in Ziploc bags, put all your samples into one larger bag and label it with the address. Then bring them into the lab. You can fill out your chain of custody form beforehand, or we can help you fill it out at our office in person.

You can also feel free to use our convenient delivery options.

How To Properly
Collect An Air Sample

The simple steps to collecting an air sample are:

  1. Place your air pump with the cassette inside each of the rooms you are testing.
  2. Run your air pump with the cassette inside. You’ll need 2,400 litres for a clearance test, and 480 litres for personal air monitoring.
  3. Remove the cassette from the pump & label it (ex: “B1 = main floor living room, B2 = 2nd floor,  washroom on north side.”)
  4. Place all cassettes in a ziplock bag and write the address location on it.
  5. Fill out our Chain of Custody form when you get to the lab.

Save Hours Delivering Asbestos Samples Using Our Automatic Asbestos Sampling Service

Air Speed

Running air at the right speed is vital. While you can get a sample quicker by turning up the pump, you can actually collapse the filter in your cassette if it’s too fast. NIOSH 7400 requires 2.5-16L/minute as the proper airflow.

You wouldn’t pump only 2.5L/minute for most air samples (it would take 16 hours to get 2,400 litres of air!). For that type of volume, you’d want to run the pump at 16L/minute (2.5 hours to finish).

Many regulators can go up to 20 L/min, but we’ve found it to be just too much air for the filters, and sometimes filters will collapse (setting you back to restart the test entirely). So try not to run the pump any higher than 16L/ min.

You need to track how long the pump was running, and what speed – down to the minute! You’ll need to write this data down on the chain of custody form when delivering the samples.

Once the pump has run enough air through the filter, put the cassette in a plastic ziplock page and label it accordingly. Here’s an example of how you might label your air samples:

  • B1 = Living room
  • B2 = Dining room
  • B3 = Upstairs bathroom

Put all your samples together in a single larger Ziploc, label the bag with the building address, and deliver them to our lab for testing. Make sure the chain of custody is in the larger bag so we know what each sample bag contains.

Air Pumps

Air sampling requires a special air pump. You need to run a certain amount of air through the cassette to get a proper reading. Some tests require 2,400 litres of air, while others only require 400.


Air samples are collected in a specialized cassette, which is a plastic tube with a filter in the bottom (it’s almost like a giant cigarette).

When air runs through the cassette, particles get stuck in the filter. When you bring the filter to us, we analyze that filter and deliver you results of that sample.


A 3-piece 25mm cassette filter – 25mm diameter, 50mm length.

Not An Expert In Sampling? 

Try Our Automatic Sampling Service

There are a lot of variables to consider to get a sample taken correctly. That’s why all air tests should be performed by a trained PCM technician (phase contrast microscopy, NIOSH 582 equivalent qualification).

If you need samples taken, but don’t have the expertise, try out our automatic sampling service. A trained PCM technician will come to the building, take the sample, and deliver test results by phone, FAX or email. You won’t have to lift a finger. Automatic sampling is available for bulk samples too.